Tony Pearson is a Master Inventor and Senior IT Architect for the IBM Storage product line at the
IBM Systems Client Experience Center in Tucson Arizona, and featured contributor
to IBM's developerWorks. In 2016, Tony celebrates his 30th year anniversary with IBM Storage. 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.
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“In times of universal deceit, telling the truth will be a revolutionary act.”
-- George Orwell
Well, it has been over two years since I first covered IBM's acquisition of the XIV company. Amazingly, I still see a lot of misperceptions out in the blogosphere, especially those regarding double drive failures for the XIV storage system. Despite various attempts to [explain XIV resiliency] and to [dispel the rumors], there are still competitors making stuff up, putting fear, uncertainty and doubt into the minds of prospective XIV clients.
Clients love the IBM XIV storage system! In this economy, companies are not stupid. Before buying any enterprise-class disk system, they ask the tough questions, run evaluation tests, and all the other due diligence often referred to as "kicking the tires". Here is what some IBM clients have said about their XIV systems:
“3-5 minutes vs. 8-10 hours rebuild time...”
-- satisfied XIV client
“...we tested an entire module failure - all data is re-distributed in under 6 hours...only 3-5% performance degradation during rebuild...”
-- excited XIV client
“Not only did XIV meet our expectations, it greatly exceeded them...”
In this blog post, I hope to set the record straight. It is not my intent to embarrass anyone in particular, so instead will focus on a fact-based approach.
Fact: IBM has sold THOUSANDS of XIV systems
XIV is "proven" technology with thousands of XIV systems in company data centers. And by systems, I mean full disk systems with 6 to 15 modules in a single rack, twelve drives per module. That equates to hundreds of thousands of disk drives in production TODAY, comparable to the number of disk drives studied by [Google], and [Carnegie Mellon University] that I discussed in my blog post [Fleet Cars and Skin Cells].
Fact: To date, no customer has lost data as a result of a Double Drive Failure on XIV storage system
This has always been true, both when XIV was a stand-alone company and since the IBM acquisition two years ago. When examining the resilience of an array to any single or multiple component failures, it's important to understand the architecture and the design of the system and not assume all systems are alike. At it's core, XIV is a grid-based storage system. IBM XIV does not use traditional RAID-5 or RAID-10 method, but instead data is distributed across loosely connected data modules which act as independent building blocks. XIV divides each LUN into 1MB "chunks", and stores two copies of each chunk on separate drives in separate modules. We call this "RAID-X".
Spreading all the data across many drives is not unique to XIV. Many disk systems, including EMC CLARiiON-based V-Max, HP EVA, and Hitachi Data Systems (HDS) USP-V, allow customers to get XIV-like performance by spreading LUNs across multiple RAID ranks. This is known in the industry as "wide-striping". Some vendors use the terms "metavolumes" or "extent pools" to refer to their implementations of wide-striping. Clients have coined their own phrases, such as "stripes across stripes", "plaid stripes", or "RAID 500". It is highly unlikely that an XIV will experience a double drive failure that ultimately requires recovery of files or LUNs, and is substantially less vulnerable to data loss than an EVA, USP-V or V-Max configured in RAID-5. Fellow blogger Keith Stevenson (IBM) compared XIV's RAID-X design to other forms of RAID in his post [RAID in the 21st Centure].
Fact: IBM XIV is designed to minimize the likelihood and impact of a double drive failure
The independent failure of two drives is a rare occurrence. More data has been lost from hash collisions on EMC Centera than from double drive failures on XIV, and hash collisions are also very rare. While the published worst-case time to re-protect from a 1TB drive failure for a fully-configured XIV is 30 minutes, field experience shows XIV regaining full redundancy on average in 12 minutes. That is 40 times less likely than a typical 8-10 hour window for a RAID-5 configuration.
A lot of bad things can happen in those 8-10 hours of traditional RAID rebuild. Performance can be seriously degraded. Other components may be affected, as they share cache, connected to the same backplane or bus, or co-dependent in some other manner. An engineer supporting the customer onsite during a RAID-5 rebuild might pull the wrong drive, thereby causing a double drive failure they were hoping to avoid. Having IBM XIV rebuild in only a few minutes addresses this "human factor".
In his post [XIV drive management], fellow blogger Jim Kelly (IBM) covers a variety of reasons why storage admins feel double drive failures are more than just random chance. XIV avoids load stress normally associated with traditional RAID rebuild by evenly spreading out the workload across all drives. This is known in the industry as "wear-leveling". When the first drive fails, the recovery is spread across the remaining 179 drives, so that each drive only processes about 1 percent of the data. The [Ultrastar A7K1000] 1TB SATA disk drives that IBM uses from HGST have specified 1.2 million hours mean-time-between-failures [MTBF] would average about one drive failing every nine months in a 180-drive XIV system. However, field experience shows that an XIV system will experience, on average, one drive failure per 13 months, comparable to what companies experience with more robust Fibre Channel drives. That's innovative XIV wear-leveling at work!
Fact: In the highly unlikely event that a DDF were to occur, you will have full read/write access to nearly all of your data on the XIV, all but a few GB.
Even though it has NEVER happened in the field, some clients and prospects are curious what a double drive failure on an XIV would look like. First, a critical alert message would be sent to both the client and IBM, and a "union list" is generated, identifying all the chunks in common. The worst case on a 15-module XIV fully loaded with 79TB data is approximately 9000 chunks, or 9GB of data. The remaining 78.991 TB of unaffected data are fully accessible for read or write. Any I/O requests for the chunks in the "union list" will have no response yet, so there is no way for host applications to access outdated information or cause any corruption.
(One blogger compared losing data on the XIV to drilling a hole through the phone book. Mathematically, the drill bit would be only 1/16th of an inch, or 1.60 millimeters for you folks outside the USA. Enough to knock out perhaps one character from a name or phone number on each page. If you have ever seen an actor in the movies look up a phone number in a telephone booth then yank out a page from the phone book, the XIV equivalent would be cutting out 1/8th of a page from an 1100 page phone book. In both cases, all of the rest of the unaffected information is full accessible, and it is easy to identify which information is missing.)
If the second drive failed several minutes after the first drive, the process for full redundancy is already well under way. This means the union list is considerably shorter or completely empty, and substantially fewer chunks are impacted. Contrast this with RAID-5, where being 99 percent complete on the rebuild when the second drive fails is just as catastrophic as having both drives fail simultaneously.
Fact: After a DDF event, the files on these few GB can be identified for recovery.
Once IBM receives notification of a critical event, an IBM engineer immediately connects to the XIV using remote service support method. There is no need to send someone physically onsite, the repair actions can be done remotely. The IBM engineer has tools from HGST to recover, in most cases, all of the data.
Any "union" chunk that the HGST tools are unable to recover will be set to "media error" mode. The IBM engineer can provide the client a list of the XIV LUNs and LBAs that are on the "media error" list. From this list, the client can determine which hosts these LUNs are attached to, and run file scan utility to the file systems that these LUNs represent. Files that get a media error during this scan will be listed as needing recovery. A chunk could contain several small files, or the chunk could be just part of a large file. To minimize time, the scans and recoveries can all be prioritized and performed in parallel across host systems zoned to these LUNs.
As with any file or volume recovery, keep in mind that these might be part of a larger consistency group, and that your recovery procedures should make sense for the applications involved. In any case, you are probably going to be up-and-running in less time with XIV than recovery from a RAID-5 double failure would take, and certainly nowhere near "beyond repair" that other vendors might have you believe.
Fact: This does not mean you can eliminate all Disaster Recovery planning!
To put this in perspective, you are more likely to lose XIV data from an earthquake, hurricane, fire or flood than from a double drive failure. As with any unlikely disaster, it is best to have a disaster recovery plan than to hope it never happens. All disk systems that sit on a single datacenter floor are vulnerable to such disasters.
For mission-critical applications, IBM recommends using disk mirroring capability. IBM XIV storage system offers synchronous and asynchronous mirroring natively, both included at no additional charge.
The marketshare data for external disk systems has been released by IDC for 4Q09. Overall, the market dropped 0.7 percent, comparing 4Q09 versus 4Q08. While EMC was quick to remind everyone that they were able to [maintain their #1 position] in the storage subset of "external disk systems", with the same 23.7 percent marketshare they had back in 4Q08 and revenues that were essentially flat, the real story concerns the shifts in the marketplace for the other major players. IBM grew revenue 9 percent, putting it nearly 5 points of marketshare ahead of HP. HP revenues dropped 7 percent, moving it further behind. Not mentioned in the [IBM Press Release] were NetApp and Dell, neck and neck for fourth place, with NetApp gaining 16.8 percent in revenues, while Dell dropped 13.5 percent. Both NetApp and Dell now have about 8 percent marketshare each. These top five storage vendors represent nearly 70 percent of the marketshare.
Given that HP is IBM's number one competitor, not just in storage but all things IT, this was a major win. Bob Evans from InformationWeek interviews my fifth-line manager, IBM executive Rod Adkins [IBM Claims Hardware Supremacy] where he shares his views and opinions about HP, Oracle-Sun, Cisco and Dell.
I'll add my two cents on what's going on:
Shift in Servers causes Shift in Storage
Hundreds of customers are moving away from HP and Sun over to IBM servers, and with it, are chosing IBM's storage offerings as well. IBM's rock-solid strategy (which I outlined in my post [Foundations and Flavorings]) has helped explain the different products and how they are positioned. HP's use of Itanium processors, and Sun's aging SPARC line, are both reasons enough to switch to IBM's lastest POWER7 processors, running AIX, IBM i (formerly i5/OS) and Linux operating systems.
Thunder in the Clouds
Some analysts predict that by 2013, one out of five companies won't even have their own IT assets. IBM supports all flavors of private, public and hybrid cloud computing models. IBM has its own strong set of offerings, is also the number one reseller of VMware, and has cloud partnerships with both Google and Amazon. HP and Microsoft have recently formed an alliance, but they have different takes on cloud computing. HP wants to be the "infrastructure" company, but Microsoft wants to focus on its ["three screens and a public cloud"] strategy. Microsoft has decided not to make its Azure Cloud operating system available for private cloud deployments. By contrast, IBM can start you with a private cloud, then help you transition to a hybrid cloud, and finally to a public cloud.
In the latest eX5 announcement, IBM's x86-based servers can run 78 percent more virtual machines per VMware license dollar. This will give IBM an advantage as HP shifts from Itanium to an all x86-based server line.
Network Attached Storage
There seems to be a shift away from FC and iSCSI towards NAS and FCoE storage networking protocols. This bodes bad for HP's acquisition of LeftHand, and Dell's acquisition of EqualLogic. IBM's SONAS for large deployments, and N series for smaller deployments, will compete nicely against HP's StorageWorks X9000 system.
Storage on Paper no longer Eco-friendly
HP beats IBM when you include consumer products like printers, which some might consider "Storage on Paper". At IBM, we often joke that 96 percent of HP's profits come from over-priced ink cartridges. With the latest focus on the environment, people are printing less. I have been printing less myself, setting my default printer to generate a PDF file instead. There are several tools available for this, including [CutePDF] and [BullZip]. As IBM employees switch from Microsoft Office to IBM's [Lotus Symphony], it has built-in "export-to-PDF" capability as well. People are also going to their local OfficeMax or CartridgeWorld to get their cartridges refilled, rather than purchase new ones. That has to be hurting HP's bottom line.
Don't Forget About Storage Management
The leading storage management suites today are IBM's Tivoli Storage Productivity Center and EMC's Control Center. HP's Storage Essentials doesn't quite beat either of these, and management software is growing in importance to more and more customers.
In addition to dominating the gaming world, producing chips for the Nintendo Wii, Sony PlayStation, and Microsoft Xbox 360, IBM also dominates the world of Linux and UNIX servers. Today, IBM announced its new POWER7 processor, and a line of servers that use this technology. Here is a quick [3-minute video] about the POWER7.
While others might be [Dancing on Sun's grave], IBM instead is focused on providing value to the marketplace. Here is another quick [2-minute video] about why thousands of companies have switched from Sun, HP and Dell over to IBM.
"With Cisco Systems, EMC, and VMware teaming up to sell integrated IT stacks, Oracle buying Sun Microsystems to create its own integrated stacks, and IBM having sold integrated legacy system stacks and rolling in profits from them for decades, it was only a matter of time before other big IT players paired off."
Once again we are reminded that IBM, as an IT "supermarket", is able to deliver integrated software/server/storage solutions, and our competitors are scrambling to form their own alliances to be "more like IBM." This week, IBM announced new ordering options for storage software with System x servers, including BladeCenter blade servers and IntelliStation workstations. Here's a quick recap:
IBM Tivoli Storage Manager FastBack v6.1 supports both Windows and Linux! FastBack is a data protection solution for ROBO (Remote Office, Branch Office) locations. It can protect Microsoft Exchange, Lotus Domino, DB2, Oracle applications. FastBack can provide full volume-level recovery, as well as individual file recovery, and in some cases Bare Machine Recovery. FastBack v6.1 can be run stand-alone, or integrated with a full IBM Tivoli Storage Manager (TSM) unified recovery management solution.
FlashCopy Manager v2.1
FlashCopy Manager uses point-in-time copy capabilities, such as SnapShot or FlashCopy, to protect application data using an application-aware approach for Microsoft Exchange, Microsoft SQL server, DB2, Oracle, and SAP. It can be used with IBM SAN Volume Controller (SVC), DS8000 series, DS5000 series, DS4000 series, DS3000 series, and XIV storage systems. When applicable, FlashCopy manager coordinates its work with Microsoft's Volume Shadow Copy Services (VSS) interface. FlashCopy Manager can provide data protection using just point-in-time disk-resident copies, or can be integrated with a full IBM Tivoli Storage Manager (TSM) unified recovery management solution to move backup images to external storage pools, such as low-cost, energy-efficient tape cartridges.
General Parallel File System (GPFS) v3.3 Multiplatform
GPFS can support AIX, Linux, and Windows! Version 3.3 adds support for Windows 2008 Server on 64-bit chipset architectures from AMD and Intel. Now you can have a common GPFS cluster with AIX, Linux and Windows servers all sharing and accessing the same files. A GPFS cluster can have up to 256 file systems. Each of these file systems can be up to 1 billion files, up to 1PB of data, and can have up to 256 snapshots. GPFS can be used stand-alone, or integrated with a full IBM Tivoli Storage Manager (TSM) unified recovery management solution with parallel backup streams.
For full details on these new ordering options, see the IBM [Press Release].
Continuing my coverage of the Data Center Conference 2009, held Dec 1-4 in Las Vegas, the title of this session refers to the mess of "management standards" for Cloud Computing.
The analyst quickly reviewed the concepts of IaaS (Amazon EC2, for example), PaaS (Microsoft Azure, for example), and SaaS (IBM LotusLive, for example). The problem is that each provider has developed their own set of APIs.
(One exception was [Eucalyptus], which adopts the Amazon EC2, S3 and EBS style of interfaces. Eucalyptus is an open-source infrastrcture that stands for "Elastic Utility Computing Architecture Linking Your Programs To Useful Systems". You can build your own private cloud using the new Cloud APIs included Ubuntu Linux 9.10 Karmic Koala termed Ubuntu Enterprise Cloud (UEC). See these instructions in InformationWeek article [Roll Your Own Ubuntu Private Cloud].)
The analyst went into specific Virtual Infrastructure (VI) and public cloud providers.
Private Clouds can be managed by VMware tools. For remote management of public IaaS clouds, there is [vCloud Express], and for SaaS, a new service called [VMware Go].
Citrix is the Open Service Champion. For private clouds based on Xen Server, they have launched the [Xen Cloud Project] to help manage. For public clouds, they have [Citrix Cloud Center, C3], including an Amazon-based "Citrix C3 Labs" for developing and testing applications. For SaaS, they have [GoToMyPC and [GoToAssist].
Amazon offers a set of Cloud computing capabilities called Amazon Web Services [AWS]. For virtual private clouds, use the AWS Management Console. For IaaS (Amazon EC2), use [CloudWatch] which includes Elastic Load Balancing.
If you prefer a common management system independent of cloud provider, or perhaps across multiple cloud providers, you may want to consider one of the "Big 4" instead. These are the top four system management software vendors: IBM, HP, BMC Software, and Computer Associates (CA).
A survey of the audience found the number one challenge was "integration". How to integrate new cloud services into an existing traditional data center. Who will give you confidence to deliver not tools for remote management of external cloud services? Survey shows:
28 percent: VI Providers (VMware, Citrix, Microsoft)
19 percent: Big 4 System Management software vendors (IBM, HP, BMC, CA)
13 percent: Public cloud providers (Amazon, Google)
40 percent: Other/Don't Know
For internal private on-promise Clouds, the results were different:
40 percent: VI Providers (VMware, Citrix, Microsoft)
21 percent: Big 4 System Management software vendors (IBM, HP, BMC, CA)
13 percent: Emerging players (Eucalyptus)
26 percent: Other/Don't Know
Some final thoughts offered by the analyst. First, nearly a third of all IT vendors disappear after two years, and the cloud will probably have similar, if not worse, track record. Traditional server, storage and network administrators should not consider Cloud technologies as a death knell for in-house on-premises IT. Companies should probably explore a mix of private and public cloud options.