Safe Harbor Statement: The information on IBM products is intended to outline IBM's general product direction and it should not be relied on in making a purchasing decision. The information on the new products is for informational purposes only and may not be incorporated into any contract. The information on IBM products is not a commitment, promise, or legal obligation to deliver any material, code, or functionality. The development, release, and timing of any features or functionality described for IBM products remains at IBM's sole discretion.
Tony Pearson is a an active participant in local, regional, and industry-specific interests, and does not receive any special payments to mention them on this blog.
Tony Pearson receives part of the revenue proceeds from sales of books he has authored listed in the side panel.
Tony Pearson is a Master Inventor and Senior IT Specialist for the IBM System Storage product line at the
IBM Executive Briefing Center in Tucson Arizona, and featured contributor
to IBM's developerWorks. In 2011, Tony celebrated his 25th year anniversary with IBM Storage on the same day as the IBM's Centennial. He is
author of the Inside System Storage series of books. This blog is for the open exchange of ideas relating to storage and storage networking hardware, software and services. You can also follow him on Twitter @az990tony.
(Short URL for this blog: ibm.co/Pearson
The IBM Storage and Storage Networking Symposium continues ...
DS8300 Benchmark for Global Mirror
Phil Allison of Fidelity National Information Services presented his success switching from competition over to IBM DS8300 disk systems for use with Global Mirror. They had usedPerformance Associates famous PAIO driver to help to the benchmarktesting. They ran the benchmars at 2x and 3x their current workloads to see how well the DS8000 performed,measuring IOPS, MB/sec, and millisecond response time (msec). They were very impressed with their results,staying below their target 0.8 msec for most of their runs.
For the Global Mirror, the did a performance "bake-off" between Ciena CN2000 versus Cisco 9216i. These areimplemented differently. Ciena uses a Layer-2 approach, encapsulating the Fibre Channel packets directlyto transport as SDH/SONET or Gigabit Ethernet (GigE), which required dedicated circuits between JacksonvilleFlorida and Little Rock, Arkansas. By contrast, Cisco uses a Layer-3 approach, encapsulating Fibre Channelpackets within an IP packet, which can leverage existing datacenter-to-datacenter backbone.
To add stress to the benchmarks, they used a "Network Impairment" emulator. These artificially inject errors,lose packets, and other signal loss conditions. Running both Cisco and Ciena under these tests help them decide which to purchase, but also enforced that idea that they made the right choice choosing IBM for theirremote distance mirroring solution.
Comparison of Bare Machine Recovery Techniques
"Bare machine recovery" is the phrase used to restore a machine that has no operating system installed (or thewrong operating system). Dave Canan from IBM Advanced Technical Support did a great job reviewing the variousproducts and techniques available, and the pros and cons of each approach. The ones he covered were:
Tivoli Storage Manager - install fresh Windows Operating System, TSM client, and then follow certain steps
Automated System Recovery(ASR) - a new feature of Windows XP and Windows 2003 works with TSM client
Symantec Ghost - formerly callled PowerQuest Drive Image, there are now two versions: Ghost Home Edition and Ghost Corporate Solution Suite
Cristie Bare Machine Recovery(CBMR) - This is an IBM partner that provides both Linux and Windows PE versions. Cristie includes a license for Windows PE, so no need to use the alternative Bart PE method.
SAN Volume Controller - Customer Experience
Bill Giles of Catholic Medical Center, a hospital in New Hampshire, presented his experienceswith IBM System Storage SAN Volume Controller. They have a mix of IBM System x, System p, andSystem i servers, as well as machines from HP, Sun, and Dell. For applications, they havePicture Archiving and Communicatiion System (PACS) for cardiology and radiology, HL7 Interface engine, Clinical Information System, TSM for backup, and Microsoft Exchange fore-mail.
They deployed SVC on AIX, Solaris, Windows 2000 and 2003. They were very delightedwith the results:
Centralized Storage Provisioning
Consolidating disparate storage into a universal platform
Enables non-disruptive data migration
Increased utilization of existing disk resources
Improved disaster recovery with FlashCopy and Metro Mirror
Birds of a Feather (BOF) sessions
We had two BOFs, one for storage attached to System z operating systems, and another for storage attached to Linux, UNIX and Windows systems. This distinctionmade sense when mainframes could only attach to CKD disks and ESCON/FICON tape,and distributed systems could only do FCP/SCSI, but these days, there are all kindsof convergence going on.
Linux on System z can now attach via FCP to LTO tape and SAN Volume Controller, allowing now a wide range of storage options for that platform. z/OS, z/VM, z/VSEand Linux on System z can all access IBM System Storage N series via NFS.
The format was traditional Q&A panel, we had experts at the front of the room,handling the questions and discussion topics brought up by the audience. I'll spareyou the individual questions and answers.
The IBM Storage and Storage Networking Symposium in Las Vegas continues ...
N series and VMware
Jeff Barnett presented how VMware manages disk image files in its VMfs repository, and how N series offersa better alternative. Virtual machines can access N series volumes directly.
Business Continuity with System i
Allison Pate presented the various Business Continuity options for System i. Many customersuse internal storage for System i, but this then hampers Business Continuity efforts. Instead,you can have IBM System Storage DS8000 or DS6000 series disk systems provide disk mirroringbetween clustered systems.
There was a lot of interest in DR550, one of our many compliance storage solutions. Ron Henkhauspresented an overview of our DR550 and DR550 Express offerings. Unlike the competitive disk-onlysolutions, such as the EMC Centera, the DR550 allows you to attach an automated tape library, managing large amounts of fixed content data at a much lower cost point. It also has encryption, for both diskand tape data.
Open Systems Disk Management
Siebo Friesenborg presented the various steps needed to troubleshoot performance problemswith open systems, including the use of "iostat" on AIX systems as an example, and the stepsyou can take to make formal Service Level Agreements (SLA) between the IT department and thevarious lines of business.
IBM Encryption - TS1120 and LTO-4 encryption comparison
Tony Abete presented TS1120 and LTO-4 encryption techniques. Deploying encryption is more thanjust choosing a tape drive. There are a variety of factors involved, such as whether to managethe keys from the application, the operating system, or the library manager. You need policiesto decided when to encrypt tapes and when not to, generating your keys, storing them, and sharingthem with your business partners, suppliers and service providers with which you send tapes.
I can tell that many people are feeling like they are "drinking from a firehose".IBM's success in storage reaches out to so many different aspects of information management,a variety of industries, and disciplines as varied as regulatory compliance and medical imaging.
Registration is now open for our next "Meet the Storage Experts" event in Second Life. All IBMers, clients and IBM Business Partners are welcome to attend. We will focus this time on DS3000 and N series disk systems, tape systems,and IBM storage networking gear.
The blog team is working on re-directs for those who don't see this in time. Depending on which RSS feed reader you use, you may need to unsubscribe/re-subscribe to re-activate. You can updatethe URL for the feed to one of these:
Continuing this week in Las Vegas, we had a great set of sessions today.
Fibre Channel Overview
I like the manner in whichJim Robinson presented this "basics" session on how Fibre Channel works, why it is spelled "Fibre" not "Fiber", and how all the different layers work in the protocol.
IBM Virtualization Engine TS7700 series
Jim Fisher from the IBM Tucson lab presented the TS7700 series, which replaces our Virtual Tape Server (VTS). Hehad performance numbers to show that it was faster in various measurements against the B20 model of the VTS. Itis supported on the z/OS, z/VM, z/VSE, TPF and z/TPF operating systems.
IBM E-mail Archiving and Storage solution
Ron Henkhaus provided an overview of IBM's E-mail Archive and Storage appliance. The solution combines IBM BladeCenter server blade, DS4200 serieswith SATA disk, and pre-installed software: IBM Content Manager, IBM Records Manager, IBM CommonStore for Lotus Domino and Microsoft Exchange, and IBM System Storage Archive Manager. Services are included to get it connected toyour e-mail environment.
Lee La Frese from our Tucson performance lab presented various performance featuresof the IBM System Storage DS8000 series, and how they compare to competition.
First, some interesting statistics.
Back in 2002, the average high-end EnterpriseStorage Server (ESS) model F20 was configured only for 4 Terabytes (TB). In 2004,the average ESS was up to 12 TB. Today, the average DS8100 is 17.4 TB and the averageDS8300 is 41.5 TB.
51 percent of DS8000 series are configured for FCP only (Linux, UNIX, Windows, i5/OS),35 percent FICON only (System z mainframe), and 14% have both mixed.
Average I/O density has stabilized to about 0.6 IOPS per GB. This means that for everyTB of business data, you can expect most applications to issue 600 Input/Output requestsper second.
While IBM SAN Volume Controller has the fastest SPC-1 and SPC-2 benchmarks, the DS8000also has good results. Looking at just the monolithic "scale-up" systems, DS8000 hasthe fastest SPC-1, and second place for SPC-2.
Compared against the EMC DMX-3, the IBM DS8000 series has superior performance.For example, comparing 2Gbps port performance on each, DMX-3 is able to do 20 IOPS perport, compared to DS8000 with 38 IOPS per port.Compared against HDS USP, the response time for 60,000 IOPS for HDS averaged 10.5 milliseconds (msec), compared to IBM DS8000 less than 6.5 msec.
There are some unique features of the DS8000 to optimize performance. Two areAdaptive Multi-stream Prefetching (AMP) which helps improve processing of databasequeries, and HyperPAV which helps on mainframe workloads.
For FATA disks, performance of sequential reads and writes is only 20 percent less than15K RPM FC disks, but a whopping 50 percent less for random access. Consider using FATAfor audio/video streaming, surveillance data, seismic recordings, and medical imaging.
Comparing 146GB 10K versus 300GB 15K from a capacity perspective was interesting.37TB of 300GB 15K had 20 percent better response time, but 25 percent less maximum throughput,than 37TB of 146GB drives. Depending on your workload, this can help decided which youchoose.
Lee also covered RAID rebuild performance. When an individual HDD fails that is part of a RAIDgroup, the DS8000 performs a rebuild onto a spare drive. A RAID-5 rebuild is processedat 52 MB/sec, compared to RAID-10 at 56 MB/sec. Rebuild processing is low priority,so any other workload will take higher priority to avoid impacting application performance.Compared to EMC, the IBM DS8000 can rebuild RAID-5 73GB 15K RPM drive in only 24 minutes, but it takes 37 minutes to do this on a DMX-3. That is 13 minutes of additional exposure where a second drive failure might cause you to lose all your data in that RAID group!
N series ILM and Business Continuity
James Goodwin from our Advanced Technical Support team presented IBM System Storage N series featuresthat relate to ILM and Business Continuity. He covered features like SnapShot, SnapLock,SnapVault and LockVault.
I have arrived safely in Las Vegas for the IBM System Storage and Storage Networking Symposium. This eventis held once every year. The gold sponsors were: Brocade, Cisco, Finisar, Servergraph, and VMware. Our silversponsor was Qlogic.
I presented IBM's System Storage strategy and an overview of our product line. For those who missed it,our strategy is focused on helping customers in four key areas:
Optimize IT - to simplify and automate your IT operations and optimize performance and functionality, through server/storage synergies, storage virtualization, and intergrated storage infrastructure management.
Leverage Information - to enable a single view of trusted business information through data sharing, and to get the most value from information through Information Lifecycle Management (ILM).
Mitigate Risk - to comply with security and regulatory requirements, and keep your business running with a complete set of business continuity solutions. IBM offers a range of non-erasable, non-rewriteable storage, encryption on disk and tape, and support for IT Infrastructure Library (ITIL) service management disciplines.
Enable Business Flexibility - to provide scalable solutions and protect your IT investment through the use of open industry standards like Storage Networking Industry Association (SNIA) Storage Management Initiative Specification (SMI-S). IBM offers scalability in three dimensions: Scale-up, Scale-out, and Scale-within.
IBM has a broad storage portfolio, in seven offering categories:
Disk Systems, including our SAN Volume Controller, DS family, and N series.
Tape Systems, including tape drives, libraries and virtualization.
Storage Networking, a complete set of switches, directors and routes
Infrastructure Management, featuring the IBM TotalStorage Productivity Center software
Business Continuity, advanced copy services and the software to manage them
Lifecycle and Retention, our non-erasable, non-rewriteable storage including DR550, N series with SnapLock, and WORM tape support, Grid Archive Manager and our Grid Medical Archive Solution (GMAS)
Storage Services, everything from consulting, design and deployment to outsourcing and hosting.
I could talk all day on this, but given that the room was packed, every seat taken and the rest of the audience standing along the walls, I had to keep it down to one hour.
SAN Volume Controller Overview
I presented an overview of the IBM System Storage SAN Volume Controller (SVC), IBM's flagship disk virtualizationproduct. Rather than giving a long laundry list of features and benefits,I focused on the five that matter most:
Reduces the cost and complexity of managing storage, especially for mixed storage environments
Simplifies Business Continuity through non-disruptive data migration and advanced copy services
Improves storage utilization, getting more value from the storage hardware you already have
Enhances personnel productivity, empowering storage administrators to get their job done
Delivers high availability and performance
SAN Volume Controller - Customer Success Stories
A good part of this conference are presented by non-IBMers, which include Business Partners and clientssharing their experiences. In this session, we had two speakers share their experiences with SVC.
David Snyder keeps over 80 web sites online and available. His digital media technologiesteam uses SVC to make their storage administration easier, and ensure high availability for web site content creation and publishing.
Mark Prybylski manages storage at his company, a financial bank. His storage management team uses SVC Global Mirror which provides asynchronous disk mirroring between different types of disk, as part oftheir Business Continuity/Disaster Recovery plan.
The last session I attended was "Storage .. to Optimize your ECM depoloyments" by Jerry Bower, now working for IBM as part of our recent acquisition of the Filenet company. ECM stands for Enterprise Content Management, and IBM is the market leader in this space. Jerry gave a great overview of IBM Content Manager software suite, our newly acquired Filenet portfolio, and the storage supported.
After the sessions was a reception at the Solution Center with dozens of exhibitor booths. For example,Optica Technologies had their PRIZM productswhich are able to connect FICON servers to ESCON storage devices.
I am back at "the Office" for a single day today. This happens often enough I need a name for it.Air Force pilots that practice landing and take-offs call them "Touch and Go", but I think I needsomething better. If you can think of a better phrase, let me know.
This week, I was in Hartford, CT, Somers, NY and our Corporate Headquarters in Armonk, in a varietyof meetings, some with editors of magazines, others with IBMers I have only spoken to over the phone andfinally got a chance to meet face to face.
I got back to Tucson last night, had meetings this morning in Second Life, then presented "InformationLifecycle Management" in Spanish to a group of customers from Mexico, Chile, and Brazil. We have a great Tucson Executive Briefing Center, and plenty of foreign-language speakers to draw from our localemployees here at the lab site.
Sunday, I leave for Las Vegas for our upcoming IBM Storage and Storage Networking Symposium. We will cover the latest in our disk, tape, storage networking and related software.Do you have your tickets? If you plan to attend, and want to meet up with me, let me know.
Last week, a writer for a magazine contacted us at IBM to confirm a quote that writing a Terabyte (TB) on disk saves 50,000 trees. I explained that this was cited from UC Berkeley's famousHow Much Information? 2003 study.
To be fair, the USA Today article explains that AT&T also offers "summary billing" as well as "on-line billing", but apparently neither of these are the default choice. I can understand that phone companies send out bills on paper because not everyone who has a phone has internet access, but in the case of its iPhone customers, internet access is in the palm of your hands! Since all iPhone customers have internet access, and AT&T knows which customers are using an iPhone, it would make sense for either on-line billing or summary billing to be the default choice, and let only those that hate trees explicitly request the full billing option.
Sending a box of 300 pages of printed paper is expensive, both for the sender and the recipient. This informationcould have been shipped less expensively on computer media, a single floppy diskette or CDrom for example. Forthose who prefer getting this level of detail, a searchable digitized version might be more useful to the consumer.
Which brings me to the concept of Information Lifecycle Management (ILM). You can read my recent posts on ILM byclicking the Lifecycle tab on the right panel, or my now infamous post from last year about ILM for my iPod.
His recollection of the history and evolution of ILM fairly matches mine:
The phrase "Information Lifecycle Management" was originally coined by StorageTek in early 1990s as a way to sell its tape systems into mainframe environments. Automated tape libraries eliminated most if not all of the concerns that disk-only vendors tout as the problem with manual tape. I began my IBM career in a product now called DFSMShsm which specifically moved data from disk to tape when it no longer needed the service level of disk. IBM had been delivering ILM offerings since the 1970s, so while StorageTek can't claim inventing the concept, we give them credit for giving it a catchy phrase.
EMC then started using the phrase four years ago in its marketing to sell its disk systems, including slower less-expensive SATA disk. The ILM concept helped EMC provide context for the many acquisitions of smaller companies that filled gaps in the EMC portfolio. Question: Why did EMC acquire company X? Answer: To be more like IBM and broaden its ILM solution portfolio.
Information Lifecycle Management is comprised of the policies, processes,practices, and tools used to align the business value of information with the mostappropriate and cost effective IT infrastructure from the time information isconceived through its final disposition. Information is aligned with businessrequirements through management policies and service levels associated withapplications, metadata, and data.
Whitepapers and other materials you might read from IBM, EMC, Sun/StorageTek, HP and others will all pretty much tell you what ILM is, consistent with this SNIA definition, why it is good for most companies, and how it is not just about buying disk and tape hardware. Software, services, and some discipline are needed to complete the implementation.
While the SNIA definition provides a vendor-independent platform to start the conversation, it can be intimidatingto some, and is difficult to memorize word for word.When I am briefing clients, especially high-level executives, they often ask for ILM to be explained in simpler terms. My simplified version is:
Information starts its life captured or entered as an "asset" ...
This asset can sometimes provide competitive advantage, or is just something needed for daily operations. Digital assets vary in business value in much the same way that other physical assets for a company might. Some assets might be declared a "necessary evil" like laptops, but are tracked to the n'th degree to ensure they are not lost, stolen or taken out of the building. Other assetsare declared "strategically important" but are readily discarded, or at least allowed to walk out the door each evening.
... then transitions into becoming just an "expense" ...
After 30-60 days, many of the pieces of information are kept around for a variety of reasons. However, if it isn'tneeded for daily operations, you might save some money moving it to less expensive storage media, throughless expensive SAN or LAN network gear, via less expensive host application servers. If you don't need instantaccess, then perhaps the 30 seconds or so to fetch it from much-less-expensive tape in an automated tape librarycould be a reasonable business trade-off.
... and ends up as a "liability".
Keeping data around too long can be a problem. In some cases, incriminating, and in other cases, just having toomuch data clogs up your datacenter arteries. If not handled properly within privacy guidelines, data potentially exposes sensitive personal or financial information of your employees and clients. Most regulations require certain data to be kept, in a manner protected against unexpected loss, unethical tampering, and unauthorized access, for a specific amount of time, after which it can be destroyed, deleted or shredded.
So ILM is not just a good idea to save a company money, it can keep them out of the court room, as well as help save the environment and not kill so many trees. Now that 100 percent of iPhone customers have internet access, and a goodnumber of non-iPhone customers have internet access at home, work, school or public library, it makes sense for companies to ask people to "opt-in" to getting their statements on paper, rather than forcing them to "opt-out".
Despite this, or perhaps because of this, over 30 percent of IBM's Linux server revenue is onnon-x86 platforms, avoiding the XenSource vs. VMware decision altogether. Both System z (traditional mainframe servers) and System p (traditional UNIX servers) are able to run many Linux images in a fully virtualized manner, without VMware or XenSource.
Philip Rosedale, chief executive of Linden Labs, which produced the Second Life virtual reality environment, said Second Life and Facebook are popular because they give people a new environment to interact in that they are comfortable with.
Of course I have blogged for months now on my involvement in Second Life, and how IBM is investing in this platform for business purposes. Recently, IBM made news for publishing its Code of Conduct,and set of guidelines on how you run your avatar in virtual worlds, including Second Life. IBM recognizesthe business potential of virtual worlds, and has formed the "3D Internet" group exploring the possibilities.Over 5000 IBM employees now use Second Life on a regular basis.
I was surprised to learn that there were over 23,000 IBMers already on Facebook. I used to be on LinkedIn,but found FaceBook to have more IBMers and have made the switch. Recently, we were told that these 23,000 IBMers spend 19 minutes, on average, per day visiting Facebook pages. Nobody askedme how much time I spend every day on FaceBook, but with over 350,000 employees in the company,I am sure some have ways to track the lives of others.
Both of these count as adding more "FUN" into the workplace, which everyone should strive for. It is also good to know that the skills you developusing Second Life or FaceBook can carry over to your next job role or your next employer.The number-one question I get from new colleagues when I mention either these exciting new ways to communicate and collaborate is: "But how is this related to business?"
Second Life is obvious, a new innovative way to hold meetings with colleagues, Business Partners and clients isgoing to have business value. Meetings in Second Life help you focus on what is being discussed, versus a plaintelephone call where your eyes may wander to other things in your view. Of course nothing beatsthe effectiveness of face-to-face meetings, but Second Life offers a more energy-efficient alternative than traveling to other cities or countries.
Stephen over at RupturedMonkey discusses the challenges of recruiting storage administrators:
There has been a Storage Admin job advertised for many months but no one wants it. Why? It's offering VERY good money but the word has got around the company has poor management practices and most people don't last for more than 6 months. So, with the shortage of good SAN people, good money and conditions, what can that company do to recruit someone? ...
This leads me to the thought that has anyone ever thought about the standards that storage administrators should follow? Can an employer look up a web site to find questions to ask prospective employees? More often than not, they are recruiting because the previous one left so how can companies know what they are getting.
There is actually a great standard called Information Technology Infrastructure Library (ITIL) that applies not just to storage administrators, but other IT personnel such as network administrators and server administrators. Here's a quick web-site about ITIL History:
ITIL History can be traced back to the late 1980’s when the British government determined that the level of IT service quality provided to them was not sufficient enough. The Central Computer and Telecommunications Agency (CCTA), now called the Office of Government Commerce (OGC), was tasked with developing a framework for efficient and financially responsible use of IT resources within the British government and the private sector.
The goal was to develop an approach that would be vendor-independent and applicable to organizations with differing technical and business needs. This resulted in the creation of the ITIL.
This standard spread from the UK to other governments in Europe, and is now being adopted worldwide by government agencies, non-profit organizations and commercial enterprises. IBM, of course, has been involved along the way, encouraging this set of best practices to take hold.
ITIL provides a common vocabulary that puts everyone in the IT industry on the same page, with the ultimate goal of helping companies run their IT organizations more efficiently.
ITIL provides recommendations, or best practices, for managing the way IT provides services to the rest of the organization, in the same way you would the rest of your business, with a defined set of processes.
While ITIL does a great job of describing what needs to be done, it doesn’t describe how to get it done. It doesn’t tell you how to take those best practices and implement them with real-life tools and technology. It’s not prescriptive.
The general process is now referred to as "IT Service Management", and the seven ITIL books are managed by the IT Service Management forum (ITSMf).
ITIL is vendor-independent. You can learn ITIL disciplines at one IT shop, and carry those skills with you when you go to another IT shop that has completely different gear. A common vocabulary would allow employers to post jobs in a consistent manner, and ask questions to those interviewing for the job. You can be ITIL-trained, and even ITIL-certified. IBM offers this training.
Of course, specific skills on how to use specific software to configure storage devices, request change control approvals, or define SAN zones, are useful, but often can be picked up on the job, reading the vendor manuals on the specifics. Of course, you can use IBM TotalStorage Productivity Center, which would allow someone to manage a variety of disk, tape and SAN fabric gear from one interface, greatly reducing the learning curve.
Some people find it surprising that it is often more cost-effective, and power-efficient, to run workloads on mainframe logical partitions (LPARs) than a stack of x86 servers running VMware.
Perhaps they won't be surprised any more. Here is an article in eWeek that explains how IBM isreducing energy costs 80% by consolidating 3,900 rack-optimized servers to 33 IBM System z mainframe servers, running Linux, in its own data centers. Since 1997, IBM has consolidated its 155 strategic worldwide data center locations down to just seven.
I am very pleased that IBM has invested heavily into Linux, with support across servers, storage, software andservices. Linux is allowing IBM to deliver clever, innovative solutions that may not be possible with other operating systems. If you are in storage, you should consider becoming more knowledgeable in Linux.
The older systems won't just end up in a landfill somewhere. Instead, the details are spelled out inthe IBM Press Release:
As part of the effort to protect the environment, IBM Global Asset Recovery Services, the refurbishment and recycling unit of IBM, will process and properly dispose of the 3,900 reclaimed systems. Newer units will be refurbished and resold through IBM's sales force and partner network, while older systems will be harvested for parts or sold for scrap. Prior to disposition, the machines will be scrubbed of all sensitive data. Any unusable e-waste will be properly disposed following environmentally compliant processes perfected over 20 years of leading environmental skill and experience in the area of IT asset disposition.
Whereas other vendors might think that some operational improvements will be enough, such as switching to higher-capacity SATA drives, or virtualizing x86 servers, IBM recognizes that sometimes more fundamental changes are required to effect real changes and real results.
I would like to welcome IBMer Barry Whyte to the blogosphere!
From his bio:
Barry Whyte is a 'Master Inventor' working in the Systems & Technology Group based in IBM Hursley, UK. Barry primarly works on the IBM SAN Volume Controller virtualization appliance. Barry graduated from The University of Glasgow in 1996 with a B.Sc (Hons) in Computing Science. In his 10 years at IBM he has worked on the successful Serial Storage Architecture (SSA) range of products and the follow-on Fibre Channel products used in the IBM DS8000 series. Barry joined the SVC development team soon after its inception and has held many positions before taking on his current role as SVC performance architect. Outside of work, Barry enjoys playing golf and all things to do with Rotary Engines.
To avoid confusion in future posts, I will refer to Barry Whyte as BarryW, and fellow EMC blogger Barry Burke (aka the Storage Anarchist) as BarryB.
I'm in Chicago this week, but it is actually HOTTER here than in my home town of Tucson, Arizona.
There are a lot of exciting conferences and events coming up soon.
SHARE will be in San Diego, August 12-17. Held twice a year, I attended SHARE for 10 years back when I was lead architect for DFSMS,and then later the focal point for storage support on the Linux for System z platform.I won't be there this time around, but am glad to see that it is still thriving.
IBM Storage and Storage Networking Symposium
IBM Storage and Storage Networking Symposium will be in Las Vegas, August 19-24.This is a great conference that is focused entirelyon the products and solutions I deal with the most. I attended nearly every one since they startedthis back in the 1990s, and am glad that I will be there this year, making several presentations.If you plan to attend this and want to meet up, drop me a note.
VMworld will be held in San Francisco, September 11-13.IBM is a top reseller of VMware software, and is proud to be a Platinum Sponsor for this event. Lookfor the panel discussion on "Storage Virtualization" which I am sure will include SAN Volume Controller.
Meet the Storage Experts
Based on our successful product launch in Second Life back in April, we are now holding meetingsevery quarter to discuss various IBM System Storage topics. The next one will be September 20 onone of the IBM islands in Second Life. For those without travel budgets to go anywhere, the advantageto our "Second Life" events is that no travel is required, it can be done from the comfort of workor home office location.
I will post updates on how to register for this event as soon as I know them.
Virtual Worlds Fall 2007 onOctober 10-11, 2007 at the San Jose Convention Center. Sandy Kearney, IBM GlobalDirector of IBM 3D Internet and Virtual Business, will be the keynote speaker.This will include discussion of Second Life.
I am sure there are others, but these are the ones that I am aware of IBM's involvement.I'll be in Chicago next week, meeting with Sales Reps and Business Partners.
The question is if this is unique or specific to these particular models, or if this affects all kinds of blade servers because of their very nature and architecture. Stephen indicates that they also have HP C class enclosures, but since they are still in test mode, cannot comment on them.
I have no experience with any of HP's blade servers, but I have worked closely with our IBM BladeCenter team to help make sure that our storage, and our SAN equipment, work well together with the BladeCenter, and more importantly, that problems can be diagnosed effectively.
When I asked why people feel they need to know the inner workings of storage, the overwhelming response was to help diagnose problems. This could include problems inplacing related data on a potentially single point of failure, problems with performance, and problems communicating with 1-800-IBM-SERV.
So, if you have encountered problems diagnosing SAN problems with BladeCenter, or find that setting up an IBM SAN with blade servers in general, I would be interested in hearing what IBM can do to make the situation better.[Read More]
Miles per Gallon measures an effeciency ratio (amount of work done with a fixed amount of energy), not a speed ratio (distance traveled in a unit of time).
Given that IOPs and MB/s are the unit of "work" a storage array does, wouldn't the MPG equivalent for storage be more like IOPs per Watt or MB/s per Watt? Or maybe just simply Megabytes Stored per Watt (a typical "green" measurement)?
You appear to be intentionally avoiding the comparison of I/Os per Second and Megabytes per Second to Miles Per Hour?
May I ask why?
This is a fair question, Barry, so I will try to address it here.
It was not a typo, I did mean MPG (miles per gallon) and not MPH (miles per hour). It is always challenging to find an analogy that everyone can relate to explain concepts in Information Technology that might be harder to grasp. I chose MPG because it was closely related to IOPS and MB/s in four ways:
MPG applies to all instances of a particular make and model. Before Henry Ford and the assembly line, cars were made one at a time, by a small team of craftsmen, and so there could be variety from one instance to another. Today, vehicles and storage systems are mass-produced in a manner that provides consistent quality. You can test one vehicle, and safely assume that all similar instances of the same make and model will have the similar mileage. The same is true for disk systems, test one disk system and you can assume that all others of the same make and model will have similar performance.
MPG has a standardized measurement benchmark that is publicly available. The US Environmental Protection Agency (EPA) is an easy analogy for the Storage Performance Council, providing the results of various offerings to chose from.
MPG has usage-specific benchmarks to reflect real-world conditions.The EPA offers City MPG for the type of driving you do to get to work, and Highway MPG, to reflect the type ofdriving on a cross-country trip. These serve as a direct analogy to SPC having SPC-1 for Online transaction processing (OLTP) and SPC-2 for large file transfers, database queries and video streaming.
MPG can be used for cost/benefit analysis.For example, one could estimate the amount of business value (miles travelled) for the amount of dollar investment (cost to purchase gallons of gasoline, at an assumed gas price). The EPA does this as part of their analysis. This is similar to the way IOPS and MB/s can be divided by the cost of the storage system being tested on SPC benchmark results. The business value of IOPS or MB/s depends on the application, but could relate to the number of transactions processed per hour, the number of music downloads per hour, or number of customer queries handled per hour, all of which can be assigned a specific dollar amount for analysis.
It seemed that if I was going to explain why standardized benchmarks were relevant, I should find an analogy that has similar features to compare to. I thought about MPH, since it is based on time units like IOPS and MB/s, butdecided against it based on an earlier comment you made, Barry, about NASCAR:
Let's imagine that a Dodge Charger wins the overwhelming majority of NASCAR races. Would that prove that a stock Charger is the best car for driving to work, or for a cross-country trip?
Your comparison, Barry, to car-racing brings up three reasons why I felt MPH is a bad metric to use for an analogy:
Increasing MPH, and driving anywhere near the maximum rated MPH for a vehicle, can be reckless and dangerous,risking loss of human life and property damage. Even professional race car drivers will agree there are dangers involved. By contrast, processing I/O requests at maximum speed poses no additional risk to the data, nor possibledamage to any of the IT equipment involved.
While most vehicles have top speeds in excess of 100 miles per hour, most Federal, State and Local speed limits prevent anyone from taking advantage of those maximums. Race-car drivers in NASCAR may be able to take advantage of maximum MPH of a vehicle, the rest of us can't. The government limits speed of vehicles precisely because of the dangers mentioned in the previous bullet. In contrast, processing I/O requests at faster speeds poses no such dangers, so the government poses no limits.
Neither IOPS nor MB/s match MPH exactly.Earlier this week,I related IOPS to "Questions handled per hour" at the local public library, and MB/s to "Spoken words per minute" in those replies. If I tried to find a metric based on unit type to match the "per second" in IOPS and MB/s, then I would need to find a unit that equated to "I/O requests" or "MB transferred" rather than something related to "distance travelled".
In terms of time-based units, the closest I could come up with for IOPS was acceleration rate of zero-to-sixty MPH in a certain number of seconds. Speeding up to 60MPH, then slamming the breaks, and then back up to 60MPH, start-stop, start-stop, and so on, would reflect what IOPS is doing on a requestby request basis, but nobody drives like this (except maybe the taxi cab drivers here in Malaysia!)
Since vehicles are limited to speed limits in normal road conditions, the closest I could come up with for MB/s would be "passenger-miles per hour", such that high-occupancy vehicles like school buses could deliver more passengers than low-occupancy vehicles with only a few passengers.
Neither start-stops nor passenger-miles per hour have standardized benchmarks, so they don't work well for comparisonbetween vehicles.If you or anyone can come up with a metric that will help explain the relevance of standardized benchmarks better than the MPG that I already used, I would be interested in it.
You also mention, Barry, the term "efficiency" but mileage is about "fuel economy".Wikipedia is quick to point out that the fuel efficiency of petroleum engines has improved markedly in recent decades, this does not necessarily translate into fuel economy of cars. The same can be said about the performance of internal bandwidth ofthe backplane between controllers and faster HDD does not necessarily translate to external performance of the disk system as a whole. You correctly point this out in your blog about the DMX-4:
Complementing the 4Gb FC and FICON front-end support added to the DMX-3 at the end of 2006, the new 4Gb back-end allows the DMX-4 to support the latest in 4Gb FC disk drives.
You may have noticed that there weren't any specific performance claims attributed to the new 4Gb FC back-end. This wasn't an oversight, it is in fact intentional. The reality is that when it comes to massive-cache storage architectures, there really isn't that much of a difference between 2Gb/s transfer speeds and 4Gb/s.
Oh, and yes, it's true - the DMX-4 is not the first high-end storage array to ship a 4Gb/s FC back-end. The USP-V, announced way back in May, has that honor (but only if it meets the promised first shipments in July 2007). DMX-4 will be in August '07, so I guess that leaves the DS8000 a distant 3rd.
This also explains why the IBM DS8000, with its clever "Adaptive Replacement Cache" algorithm, has such highSPC-1 benchmarks despite the fact that it still uses 2Gbps drives inside. Given that it doesn't matter between2Gbps and 4Gbps on the back-end, why would it matter which vendor came first, second or third, and why call it a "distant 3rd" for IBM? How soon would IBM need to announce similar back-end support for it to be a "close 3rd" in your mind?
I'll wrap up with you're excellent comment that Watts per GB is a typical "green" metric. I strongly support the whole"green initiative" and I used "Watts per GB" last month to explain about how tape is less energy-consumptive than paper.I see on your blog you have used it yourself here:
The DMX-3 requires less Watts/GB in an apples-to-apples comparison of capacity and ports against both the USP and the DS8000, using the same exact disk drives
It is not clear if "requires less" means "slightly less" or "substantially less" in this context, and have no facts from my own folks within IBM to confirm or deny it. Given that tape is orders of magnitude less energy-consumptive than anything EMC manufacturers today, the point is probably moot.
I find it refreshing, nonetheless, to have agreed-upon "energy consumption" metrics to make such apples-to-apples comparisons between products from different storage vendors. This is exactly what customers want to do with performance as well, without necessarily having to run their own benchmarks or work with specific storage vendors. Of course, Watts/GB consumption varies by workload, so to make such comparisons truly apples-to-apples, you would need to run the same workload against both systems. Why not use the SPC-1 or SPC-2 benchmarks to measure the Watts/GB consumption? That way, EMC can publish the DMX performance numbers at the same time as the energy consumption numbers, and then HDS can follow suit for its USP-V.
I'm on my way back to the USA soon, but wanted to post this now so I can relax on the plane.
Wrapping up this week's exploration on disk system performance, today I willcover the Storage Performance Council (SPC) benchmarks, and why I feel they are relevant to help customers make purchase decisions. This all started to address a comment from EMC blogger Chuck Hollis, who expressed his disappointment in IBM as follows:
You've made representations that SPC testing is somehow relevant to customers' environments, but offered nothing more than platitudes in support of that statement.
Apparently, while everyone else in the blogosphere merely states their opinions and moves on,IBM is held to a higher standard. Fair enough, we're used to that.Let's recap what we covered so far this week:
Monday, I explained how seemingly simple questions like "Which is the tallestbuilding?" or "Which is the fastest disk system?" can be steeped in controversy.
Tuesday, I explored what constitutes a disk system. While there are special storage systemsthat include HDD that offer tape-emulation, file-oriented access, or non-erasable non-rewriteable protection,it is difficult to get apples-to-apples comparisions with storage systems that don't offer these special features.I focused on the majority of general-purpose disk systems, those that are block-oriented, direct-access.
Today, I will explore ways to apply these metrics to measure and compare storageperformance.
Let's take, for example, an IBM System Storage DS8000 disk system. This has a controller thatsupports various RAID configurations, cache memory, and HDD inside one or more frames.Engineers who are testing individual components of this system might run specifictypes of I/O requests to test out the performance or validate certain processing.
100% read-hit, this means that all the I/O requests are to read data expectedto be in the cache.
100% read-miss, this means that all the I/O requests are to read data expectedNOT to be in the cache, and must go fetch the data from HDD.
100% write-hit, this means that all the I/O requests are to write data into cache.
100% write-miss, this means that all the I/O requests are to bypass the cache,and are immediately de-staged to HDD. Depending on the RAID configuration, this can result in actually reading or writing several blocks of data on HDD to satisfy thisI/O request.
Known affectionately in the industry as the "four corners" test, because you can show them on a box, with writes on the left, reads on the right,hits on the top, and misses on the bottom.Engineers are proud of these results, but these workloads do notreflect any practical production workload. At best, since all I/O requests are oneof these four types, the four corners provide an expectation range from the worst performance (most often write-missin the lower left corner)and the best performance (most often read-hit in the upper right corner) you might get with a real workload.
To understand what is needed to design a test that is more reflective of real business conditions,let's go back to yesterday's discussion of fuel economy of vehicles, with mileage measured in miles per gallon.The How Stuff Works websiteoffers the following description for the two measurements taken by the EPA:
The "city" program is designed to replicate an urban rush-hour driving experience in which the vehicle is started with the engine cold and is driven in stop-and-go traffic with frequent idling. The car or truck is driven for 11 miles and makes 23 stops over the course of 31 minutes, with an average speed of 20 mph and a top speed of 56 mph.
The "highway" program, on the other hand, is created to emulate rural and interstate freeway driving with a warmed-up engine, making no stops (both of which ensure maximum fuel economy). The vehicle is driven for 10 miles over a period of 12.5 minutes with an average speed of 48 mph and a top speed of 60 mph.
Why two different measurements? Not everyone drives in a city in stop-and-go traffic. Having only one measurement may not reflect the reality that you may travel long distances on the highway. Offering both city and highway measurements allows the consumers to decide which metric relates closer to their actual usage.
Should you expect your actual mileage to be the exact same as the standardized test?Of course not. Nobody drives exactly 11 miles in the city every morning with 23 stops along the way,or 10 miles on the highway at the exact speeds listed.The EPA's famous phrase "your mileage may vary" has been quickly adopted into popular culture's lexicon. All kinds of factors, like weather, distance, anddriving style can cause people to get better or worse mileage than thestandardized tests would estimate.
Want more accurate results that reflect your driving pattern, in specific conditions that you are most likely to drive in? You could rentdifferent vehicles for a week and drive them around yourself, keeping track of whereyou go, and how fast you drove, and how many gallons of gas you purchased, so thatyou can then repeat the process with another rental, and so on, and then use yourown findings to base your comparisons. Perhaps you find that your results are always20% worse than EPA estimates when you drive in the city, and 10% worse when you driveon the highway. Perhaps you have many mountains and hills where you drive, you drive too fast, you run the Air Conditioner too cold, or whatever.
If you did this with five or more vehicles, and ranked them best to worstfrom your own findings, and also ranked them best to worst based on the standardizedresults from the EPA, you likely will find the order to be the same. The vehiclewith the best standardized result will likely also have the best result from your ownexperience with the rental cars. The vehicle with the worst standardized result willlikely match the worst result from your rental cars.
(This will be one of my main points, that standardized estimates don't have to be accurate to beuseful in making comparisons. The comparisons and decisions you would make with estimatesare the same as you would have made with actual results, or customized estimates based on current workloads. Because the rankings are in the same order, they are relevant and useful for making decisions based on those comparisons.)
Most people shopping around for a new vehicle do not have the time or patience to do this with rental cars. Theycan use the EPA-certified standardized results to make a "ball-park" estimate on how much they will spendin gasoline per year, decide only on cars that might go a certain distancebetween two cities on a single tank of gas, or merely to provide ranking of thevehicles being considered. While mileage may not be the only metric used in making a purchase decision, it can certainly be used to help reduce your consideration setand factor in with other attributes, like number of cup-holders, or leather seats.
In this regard, the Storage Performance Council has developed two benchmarks that attempt to reflect normal business usage, similar to "City" and "Highway" driving measurements.
SPC-1 consists of a single workload designed to demonstrate the performance of a storage subsystem while performing the typical functions of business critical applications. Those applications are characterized by predominately random I/O operations and require both queries as well as update operations. Examples of those types of applications include OLTP, database operations, and mail server implementations.
SPC-2 consists of three distinct workloads designed to demonstrate the performance of a storage subsystem during the execution of business critical applications that require the large-scale, sequential movement of data. Those applications are characterized predominately by large I/Os organized into one or more concurrent sequential patterns. A description of each of the three SPC-2 workloads is listed below as well as examples of applications characterized by each workload.
Large File Processing: Applications in a wide range of fields, which require simple sequential process of one or more large files such as scientific computing and large-scale financial processing.
Large Database Queries: Applications that involve scans or joins of large relational tables, such as those performed for data mining or business intelligence.
Video on Demand: Applications that provide individualized video entertainment to a community of subscribers by drawing from a digital film library.
The SPC-2 benchmark was added when people suggested that not everyone runs OLTP anddatabase transactional update workloads, just as the "Highway" measurement was addedto address the fact that not everyone drives in the City.
If you are one of the customers out there willing to spend the time and resources to do your own performance benchmarking, either at your own data center, or with theassistance of a storage provider, I suspect most, if not all, the major vendors(including IBM, EMC and others), and perhaps even some of the smaller start-ups, would be glad to work with you.
If you want to gather performance data of your actual workloads, and use this to estimate how your performance might be with a new or different storage configuration, IBMhas tools to make these estimates, and I suspect (again) that most, if not all, of theother storage vendors have developed similar tools.
For the rest of you who are just looking to decide which storage vendors to invite on your next RFP, and which products you might like to investigate that matchthe level of performance you need for your next project or application deployment,than the SPC benchmarks might help you with this decision. If performance is importantto you, factor these benchmark comparisons with the rest of the attributes you arelooking for in a storage vendor and a storage system.
In my opinion, I feel that for some people, the SPC benchmarks provide some value in this decision making process. They are proportionally correct, in that even ifyour workload gets only a portion of the SPC estimate, that storage systems withfaster benchmarks will provide you better performance than storage systems with lower benchmark results. That is why I feel they can be relevant in makingvalid comparisons for purchase decisions.
Hopefully, I have provided enough "food for thought"on this subject to support why IBM participates in the Storage Performance Council, why the performance of the SAN Volume Controller can be compared to the performanceof other disk systems, and why we at IBM are proud of the recent benchmark results in our recent press release.
Continuing our exploration this week into the performance of disk systems, today I will cover the metrics to measure performance. Why do people have metrics?
Help provide guidance in decision making prior to purchase
Help manage your current environment
Help drive changes
Several bloggers suggested that perhaps an analogy to vehicles would be reasonable, given that cars and trucks are expensive pieces of engineering equipment, and people make purchase decisions between different makes and models.
In the United States, the Environmental Protection Agency (EPA) government entity is responsible for measuringfuel economy of vehicles using the metric Miles Per Gallon (mpg).Specifically, these are U.S. miles (not nautical miles) and U.S. gallons, not imperial gallons. It is importantwhen defining metrics that you are precise on the units involved.
Since nearly all vehicles are driven by gallons of gasoline, and travel miles of distance, this is a great metric to use for comparing all kinds of vehicles, including motorcycles, cars, trucks and airplanes. The EPA has a fuel economy website to help people make these comparisons.Manufacturers are required by law to post their vehicles' fuel-economy ratings, as certified by the federal Environmental Protection Agency (EPA), on the window stickers of most every new vehicle sold in the U.S. -- vehicles that have gross-vehicle-weight ratings over 8,500 pounds are the exception.
What about storage performance? What could we use as the "MPG"-like metric that would allow you to compare different makes and models of storage?
The two most commonly used are I/O requests per second (IOPS) and Megabytes transferred per second (MB/s). To understand the difference in each one, let's go back to our analogy from yesterday's post.
(A woman calls the local public library. She picks up the phone, and dials the phone number of the one down the street. A man working at the library hears the phone ring, answers it with "Welcome to the Public Library! How can I help you?" She asks "What is the capital city of Ethiopia?" He replies "Addis Ababa" and hangs up. Satisfied with this response, she hangs up. In this example, the query for information was the I/O request, initiated by the lady, to the public library target)
In this example, it might have only taken 1 second to actually provide the answer, but it might have taken 10-30 seconds to pick up the phone, hear the request, respond, and then hang up the phone. If one person is able to do this in 10 seconds, on average, then he can handle 360 questions per hour. If another person takes 30 seconds, then only 120 questions per hour. Many business applications read or write less than 4KB of information per I/O request, and as such the dominant factor is not the amount of time to transfer the data, but how quickly the disk system can respond to each request. IOPS is very much like counting "Questions handled per hour" at the public library. To be more specific on units, we may specify the specific block size of the request, say 512 bytes or 4096 bytes, to make comparisons consistent.
Now suppose that instead of asking for something with a short answer, you ask the public library to read you the article from a magazine, identify all the movies and show times of a local theatre, or recite a work from Shakespeare. In this case, the time it took to pick up the phone and respond is very small compared to the time it takes to deliverthe information, and could be measured instead in words per minute. Some employees of the library may be faster talkers, having perhaps worked in auction houses in a prior job, and can deliver more words per minute than other employees. MB/s is very much like counting "Spoken words per minute" at the public library. To be more specific on units, we may request a specific amount of information, say the words contained in "Romeo and Juliet", to make comparisons consistent.
Now that we understand the metrics involved, tomorrow we can discuss how to use these in the measurement process.
Yesterday, I started this week's topic discussing the various areas of exploration to helpunderstand our recent press release of the IBM System Storage SAN Volume Controller and itsimpressive SPC-1 and SPC-2 benchmark results that ranks it the fastest disk system in the industry.
Some have suggested that since the SVC has a unique design, it should be placed in its own category,and not compared to other disk systems. To address this, I would like to define what IBM meansby "disk system" and how it is comparable to other disk systems.
When I say "disk system", I am going to focus specifically on block-oriented direct-access storage systems, which I will define as:
One or more IT components, connected together, that function as a whole, to serve as a target forread and write requests for specific blocks of data.
Clarification: One could argue, and several do in various comments below, that there are other typesof storage systems that contain disks, some that emulate sequential access tape libraries, some that emulate file-systems through CIFS or NFS protocols, and some that support thestorage of archive objects and other fixed content. At the risk of looking like I may be including or excluding such to fit my purposes, I wanted to avoid apples-to-orangescomparisons between very different access methods. I will limit this exploration to block-oriented, direct-access devices. We can explore these other types of storage systems in later posts.
People who have been working a long time in the storage industry might be satisfied by this definition, thinkingof all the disk systems that would be included by this definition, and recognize that other types of storage liketape systems that are appropriately excluded.
Others might be scratching their heads, thinking to themselves "Huh?" So, I will provide some background, history, and additional explanation. Let's break up the definition into different phrases, and handle each separately.
read and write requests
Let's start with "read and write requests", which we often lump together generically as input/output request, or just I/O request. Typically an I/O request is initiated by a host, over a cable or network, to a target. The target responds with acknowledgment, data, or failure indication. A host can be a server, workstation, personal computer, laptop or other IT device that is capable of initiating such requests, and a target is a device or system designed to receive and respond to such requests.
(An analogy might help. A woman calls the local public library. She picks up the phone, and dials the phone number of the one down the street. A man working at the library hears the phone ring, answers it with "Welcome to the Public Library! How can I help you?" She asks "What is the capital city of Ethiopia?" and replies "Addis Ababa." and hangs up. Satisfied with this response, she hangs up. In this example, the query for information was the I/O request, initiated by the lady, to the public library target)
Today, there are three popular ways I/O requests are made:
CCW commands over OEMI, ESCON or FICON cables
SCSI commands over SCSI, Fibre Channel or SAS cables
SCSI commands over Ethernet cables, wireless or other IP communication methods
specific blocks of data
In 1956, IBM was the first to deliver a disk system. It was different from tape because it was a "direct access storage device" (the acronym DASD is still used today by some mainframe programmers). Tape was a sequential media, so it could handle commands like "read the next block" or "write the next block", it could not directly read without having to read past other blocks to get to it, nor could it write over an existing block without risking overwriting the contents of blocks past it.
The nature of a "block" of data varies. It is represented by a sequence of bytes of specific length. The length is determined in a variety of ways.
CCW commands assume a Count-Key-Data (CKD) format for disk, meaning that tracks are fixed in size, but that a track can consist of one or more blocks, and can be fixed or variable in length. Some blocks can span off the end of one track, and over to another track. Typical block sizes in this case are 8000 to 22000 bytes.
SCSI commands assume a Fixed-Block-Architecture (FBA) format for disk, where all blocks are the same size, almost always a power of two, such as 512 or 4096 bytes. A few operating systems, however, such as i5/OS on IBM System i machines, use a block size that doesn't follow this power-of-two rule.
one or more IT components
You may find one or more of the following IT components in a disk system:
motorized platter(s) covered in magnetic coating with a read/write head to move over its surface. These are often referred to as Hard Disk Drive (HDD) or Disk Drive Modules (DDM), and are manufacturedby companies like Seagate or Hitachi Global Storage Technologies.
A set of HDD can be accessed individually, affectionately known as JBOD for Just-a-bunch-of-disk, or collectively in a RAID configuration.
Memory can act as the high-speed cache in front of slower storage, or as the storage itself. For example, the solid state disk that IBM announced last week is entirely memory storage, using Flash technology.
Lately, there are two popular packaging methods for disk systems:
Monolithic -- all the components you need connected together inside a big refrigerator-sized unit, with options to attach additional frames. The IBM System Storage DS8000, EMC Symmetrix DMX-4 and HDS TagmaStore USP-V all fit this category.
Modular -- components that fit into standard 19-inch racks, often the size of the vegetable drawer inside a refrigerator, that can be connected externally with other components, if necessary, to make a complete disk system. The IBM System Storage DS6000, DS4000, and DS3000 series, as well as our SVC and N series, fall into this category.
Regardless of packaging, the general design is that a "controller" receives a request from its host attachment port, and uses its processors and cache storage to either satisfy the request, or pass the request to the appropriate HDD,and the results are sent back through the host attachment port.
In all of the monolithic systems, as well as some of the modular ones, the controller and HDD storage are contained in the same unit. On other modular systems, the controller is one system, and the HDD storage is in a separate system, and they are cabled together.
serve as a target
The last part is that a disk system must be able to satisfy some or all requests that come to it.
(Using the same analogy used above, when the lady asked her question, the guy at the public library knew the answer from memory, and replied immediately. However, for other questions, he might need to look up the answer in a book, do a search on the internet, or call another library on her behalf.)
Some disk systems are cache-only controllers. For these, either the I/O request is satisfied as a read-hit or write-hit in cache, or it is not, and has to go to the HDD. The IBM DS4800 and N series gateways are examples of this type of controller.
Other systems may have controller and disk, but support additional disk attachment. In this case, either the I/O request is handled by the cache or internal disk, or it has to go out to external HDD to satisfy the request. IBM DS3000 series, DS4100, DS4700, and our N series appliance models, all fall into this category.
So, the SAN Volume Controller is a disk system comprising of one to four node-pairs. Each node is a piece of IT equipment that have processors and cache. These node-pairs are connected to a pair of UPS power supplies to protect the cache memory holding writes that have not yet been de-staged. The combination of node-pairs and UPS acting as a whole, is able to serve as a target to SCSI commands sent over Fibre Channel cables on a Storage Area Network (SAN). To read some blocks of data, it uses its internal cache storage to satisfy the request, and for others, it goes out to external disk systems that contain the data required. All writes are satisfied immediately in cache on the SVC, and later de-staged to external disk when appropriate.
As of end of 2Q07, having reached our four-year anniversary for this product, IBM has sold over 9000 SVC nodes, which are part of more than 3100 SVC disk systems. These things are flying off the shelves, clocking in a 100% YTY growth over the amount we sold twelve months ago. Congratulations go to the SVC development team for their impressive feat of engineering that is starting to catch the attention of many customers and return astounding results!
So, now that I have explained why the SVC is considered a disk system, tomorrow I'll discuss metrics to measure performance.
Continuing my business trip through Asia, I have left Chengdu, China, and am now in Kuala Lumpur, Malaysia.
On Sunday, a colleague and I went to the famous Petronas Twin Towers, which a few years ago were officially the tallestbuildings in the world. If you get there early enough in the day, and wait in line for a few hours, you can get a ticket permitting you to go up to the "Skybridge" on the 41st floor that connects the two buildings. The views are stunning, and I am glad to have done this.(If you are afraid of heights, get cured by facing your fears with skydiving)
You would think that a question as simple as "Which is the tallest building in the world?" could easily be answered, given that buildings remain fixed in one place and do not drastically shrink or get taller over time or weather conditions, and the unit of height, the "meter", is an officially accepted standard in all countries, defined as the distance traveled by light in absolute vacuum in 1/299,792,458 of a second.
The controversy stems around two key areas of dispute:
What constitutes a building?
A building is a structure intended for continuous human occupancy, as opposed to the dozens ofradio and television broadcasting towers which measure over 600 meters in height. The Petronas Twin Towers is occupied by a variety of business tenants and would qualify as a building. Radio and Television towers are not intended for occupation, and should not be considered.
Where do you start measuring, and where do you stop?
Since 1969, the height was generally based on a building's height from the sidewalk level of the main entrance to the architectural top of the building. The "architectural top" included towers, spires (but not antennas), masts or flagpoles. Should the measurements be only to the top to the highest inhabitable floor?
What if the building has many more floors below ground level? What if the building exists in a body of water, should sidewalk level equate to water level, and at low tide or high tide? (Laugh now, but this might happen sooner than you think!)
To bring some sanity to these comparisons, the Council on Tall Buildings and Urban Habitat has tried to standardize the terms and definitions to makecomparisons between buildings fair. Why does all this matter whose building is tallest? It matters in twoways:
People and companies are willing to pay more to be a tenant in tall towers, affording a luxurious bird's-eyeview to impress friends, partners and clients, and so the rankings can influence purchase or leasing prices of floorspace in these buildings.
Architects and engineers involved in building these structures want to list these on their resume.These buildings are an impressive feat of engineering, and the teams involved collaborate in a global mannerto accomplish them. If an architecture or engineeering company can build the world's tallest building, you can trust themto build one for you. The rankings can help drive revenues in generating demand for services and offerings.
What does any of this have to do with storage? Two weeks ago, IBM and the Storage Performance Councilanswered the question "Which is the fastest disk system?" with apress release. Customers thatcare about performance of their most mission critical applications are often willing to pay a premium to run theirapplications on the fastest disk system, and the IBM System Storage SAN Volume Controller, built through aglobal collaboration of architects and engineers across several countries, is (in my opinion at least) an impressive feat of storage engineering.