“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...”
-- delighted XIV client
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.
For more about IBM XIV reliability, read this whitepaper [IBM XIV© Storage System: Reliability Reinvented]. To find out why so many clients LOVE their XIV, contact your local IBM storage sales rep or IBM Business Partner.
technorati tags: IBM, XIV, DDF, RAID-5, RAID-10, RAID-X, RAID-6, RAID-DP, HP, EVA, HDS, USP-V, EMC, CLARiiON, V-Max, Disaster Recovery, HGST, UltraStar, A7K1000
I nearly fell out of my chair laughing.
Nigel Poulton over at Ruptured Monkey suggests a variety of nick names for the various storage bloggers, in his post[Storage Blogwars and the Vendor Fight Club].
Of these, fellow blogger Marc Farley suggested for me "Tony Late for Dinner Pearson", which is fair, I guess, given that I often work late to make sure my blog posts are well written, and sometimes that means I am the last to leave the building.
Full Disclosure: I've known Marc for a while now, we have attended events together and even were co-speakers on a conference call for customers.
Perhaps more disturbing is that, for the most part, the storage blogosphere is entirely dominated by men. Where are the women bloggers for storage?
technorati tags: IBM, Late For Dinner, Marc Farley, Nigel Poulton, RupturedMonkey
People are confused over various orders of magnitude. News of the economic meltdownoften blurs the distinction between millions (10^6
), billions (10^9
), and trillions (10^12
).To show how different these three numbers are, consider the following:
- A million seconds ago - you might have received your last paycheck (12 days)
- A billion seconds ago - you were born or just hired on your current job (31 years)
- A trillion seconds ago - cavemen were walking around in Asia (31,000 years)
|That these numbers confuse the average person is no surprise, but that it confuses marketing people in the storage industry is even more hilarious. I am often correcting people who misunderstandMB (million bytes), GB (billion bytes) and TB (trillion bytes) of information.Take this graph as an example from a recent presentation.|
At first, it looks reasonable, back in 2004, black-and-white 2D X-Ray images were only 1MBin size when digitized, but by 2010 there will be fancy 4D images that now take 1TB, representinga 1000x increase. What?When I pointed out this discrepancy, the person who put this chart together didn't know what to fix.Were 4D images only 1GB in size, or was it really a 1000000x increase.
If a 2D image was 1000 by 1000 pixels, each pixel was a byte of information, then a 3D imagemight either be 1000 by 1000 by 1000 [voxels], or 1000 by 1000 at 1000 frames per second (fps). Thefirst being 3D volumetric space, and the latter called 2D+time in the medical field, the rest of us just say "video".4D images are 3D+time, volumetric scans over time, so conceivably these could be quite large in size.
The key point is that advances in medical equipment result in capturing more data, which canhelp provide better healthcare. This would be the place I normally plug an IBM product, like the Grid Medical Archive Solution [GMAS], a blended disk and tape storage solution designed specifically for this purpose.
So, as government agencies look to spend billions of dollars to provide millions of peoplewith proper healthcare, choosing to spend some of this money on a smarter infrastructure can result in creating thousands of jobs and save everyone a lot of money, but more importantly, save lives.
For more on this, check out Adam Christensen's blog post on[Smarter Planet], which points to a podcast byDr. Russ Robertson, chairman of the Counsel of Medical Education at Northwestern University’s Feinberg School of Medicine, and Dan Pelino, general manager of IBM's Healthcare and Life Sciences Industry.
technorati tags: IBM, smarter healthcare, 2D+time, 3D+time, 4D, medical images, Adam Christensen, Russ Robertson, Dan Pelino
Wrapping up this week's theme on ways to make the planet smarter, and less confusing, I present IBM's third annual [five in five
]. These are five IBM innovations to watch over the next five years, all of which have implications on information storage. Here is a quick [3-minute video
] that provides the highlights:
technorati tags: IBM, five-in-five, innovations, solar, health, talking Web, shopping assistants, forgetting
This week is Thanksgiving holiday in the USA, so I thought a good theme would be things I am thankful for.
I'll start with saying that I am thankful EMC has finally announcedAtmos last week. This was the "Maui" part of the Hulk/Maui rumors we heard over a year ago. To quickly recap, Atmos is EMC's latest storage offeringfor global-scale storage intended for Web 2.0 and Digital Archive workloads. Atmos can be sold as just software, or combined with Infiniflex,EMC's bulk, high-density commodity disk storage systems. Atmos supports traditionalNFS/CIFS file-level access, as well as SOAP/REST object protocols.
I'm thankful for various reasons, here's a quick list:
- It's hard to compete against "vaporware"
Back in the 1990s, IBM was trying to sell its actual disk systems against StorageTek's rumored "Iceberg" project. It took StorageTek some four years to get this project out,but in the meantime, we were comparing actual versus possibility. The main feature iswhat we now call "Thin Provisioning". Ironically, StorageTek's offering was not commercially successful until IBM agreed to resell this as the IBM RAMAC Virtual Array (RVA).
Until last week, nobody knew the full extent of what EMC was going to deliver on the many Hulk/Maui theories. Severalhinted as to what it could have been, and I am glad to see that Atmos falls short of those rumored possibilities. This is not to say that Atmos can't reach its potential, and certainly some of the design is clever, such as offering native SOAP/REST access.
Instead, IBM now can compare Atmos/Infiniflex directly to the features and capabilities of IBM's Scale Out File Services [SoFS], which offers a global-scale multi-site namespace with policy-based data movement, IBM System Storage Multilevel Grid Access Manager[GAM] that manages geographical distrubuted information,and IBM [XIV Storage System] that offers high-density bulk storage.
- Web 2.0 and Digital Archive workloads justify new storage architectures
When I presented SoFS and XIV earlier this year, I mentioned they were designed forthe fast-growing Web 2.0 and Digital Archive workloads that were unique enough to justify their own storage architectures. One criticism was that SoFS appeared to duplicate what could be achieved with dozens of IBM N series NAS boxes connected with Virtual File Manager (VFM). Why invent a new offering with a new architecture?
With the Atmos announcement, EMC now agrees with IBM that the Web 2.0 and DigitalArchive workloads represent a unique enough "use case" to justify a new approach.
- New offerings for new workloads will not impact existing offerings for existing workloads
I find it amusing that EMC is quickly defending that Atmos will not eat into its DMXbusiness, which is exactly the FUD they threw out about IBM XIV versus DS8000 earlier this year. In reality, neither the DS8000 nor the DMX were used much for Web 2.0 andDigital Archive workloads in the past. Companies like Google, Amazon and others hadto either build their own from piece parts, or use low-cost midrange disk systems.
Rather, the DS8000 and DMX can now focus on the workloads they were designed for,such as database applications on mainframe servers.
- Cloud-Oriented Storage (COS)
Just when you thought we had enough terminology already, EMC introduces yet another three-letter acronym [TLA]. Kudos to EMC for coining phrases to help move newconcepts forward.
Now, when an RFP asks for Cloud-oriented storage, I am thankful this phrase will help serve as a trigger for IBM to lead with SoFS and XIV storage offerings.
- Digital archives are different than Compliance Archives
EMC was also quick to point out that object-storage Atmos was different from theirobject-storage EMC Centera. The former being for "digital archives" and the latter for"compliance archives". Different workloads, Different use cases, different offerings.
Ever since IBM introduced its [IBM System Storage DR550] several years ago, EMC Centera has been playing catch-up to match IBM'smany features and capabilities. I am thankful the Centera team was probably too busy to incorporate Atmos capabilities, so it was easier to make Atmos a separate offering altogether. This allows the IBM DR550 to continue to compete against Centera's existingfeature set.
- Micro-RAID arrays, logical file and object-level replication
I am thankful that one of the Atmos policy-based feature is replicating individualobjects, rather than LUN-based replication and protection. SoFS supports this forlogical files regardless of their LUN placement, GAM supports replication of files and medical images across geographical sites in the grid, and the XIV supports this for 1MBchunks regardless of their hard disk drive placement. The 1MB chunk size was basedon the average object size from established Web 2.0 and DigitalArchive workloads.
I tried to explain the RAID-X capability of the XIV back in January, under muchcriticism that replication should only be done at the LUN level. I amthankful that Marc Farley on StorageRap coined the phrase[Micro-RAID array] to helpmove this new concept further. Now, file-level, object-level and chunk-level replication can be considered mainstream.
- Much larger minimum capacity increments
The original XIV in January was 51TB capacity per rack, and this went up to 79TB per rack for the most recent IBM XIV Release 2 model. Several complained that nobody would purchase disk systems at such increments. Certainly, small and medium size businessesmay not consider XIV for that reason.
I am thankful Atmos offers 120TB, 240TB and 360TB sizes. The companies that purchasedisk for Web 2.0 and Digital Archive workloads do purchase disk capacity in these large sizes. Service providers add capacity to the "Cloud" to support many of theirend-clients, and so purchasing disk capacity to rent back out represents revenue generating opportunity.
- Renewed attention on SOAP and REST protocols
IBM and Microsoft have been pushing SOA and Web Services for quite some time now.REST, which stands for [Representational State Transfer] allows static and dynamic HTML message passing over standard HTTP.SOAP, which was originally [Simple Object Access Protocol], and then later renamed to "Service Oriented Architecture Protocol", takes this one step further, allowingdifferent applications to send "envelopes" containing messages and data betweenapplications using HTTP, RPC, SMTP and a variety of other underlying protocols.Typically, these messages are simple text surrounded by XML tags, easily stored asfiles, or rows in databases, and served up by SOAP nodes as needed.
- It's hard to show leadership until there are followers
IBM's leadership sometimes goes unnoticed until followerscreate "me, too!" offerings or establish similar business strategies. IBM's leadership in Cloud and Grid computing is no exception.Atmos is the latest me-too product offering in this space, trying pretty muchto address the same challenges that SoFS and XIV were designed for.
So, perhaps EMC is thankful that IBM has already paved the way, breaking throughthe ice on their behalf. I am thankful that perhaps I won't have to deal with as much FUD about SoFS, GAM and XIV anymore.
technorati tags: IBM, SoFS, XIV, GAM, DS8000, EMC, Atmos, Hulk, Maui, Infiniflex, STK, StorageTek, Iceberg, RVA, thin provisioning, VFM, SOAP, REST, DMX, RAID-X, Micro-RAID