IBM Storage UK Has Codified Stupidity

cod·i·fy  (kd-f, kd-)

tr.v. cod·i·fied, cod·i·fy·ing, cod·i·fies

1. To reduce to a code: codify laws.

2. To arrange or systematize.

Pay attention to number 2 there. Chris Mellor of The Register got some words from Steve Legg, IBM UK’s Chief Technology Officer for Storage.

These words made it quite clear that it there's an intent to codify stupidity within IBM Storage UK. He said simplify, but this is me, and I don’t like lies and obfuscation. What he actually meant is “collapse the offerings, and then make some patently ridiculous and arguably false statements to the press.” The word choices he made were exceptionally poor, but the choices made in "collapsing" are far worse. 

And here comes the hatemail because me, Mister I-Love-SVC and I-Love-DS8K is calling IBM Storage “stupid” and “ridiculous” and thus I must now be a shill for $MostHatedVendor or whatever. Except I’m STILL not employed or representing anybody but myself. Seriously, if I was shilling, I would have built myself a Dragon 20w with dual 5970’s. Or I would have at least put 16GB in my ESXi box instead of 8GB.

Anyways, let’s be honest and start with the good. I like honest, and I like good. Who doesn’t? SONAS – forget IBM’s acronym of Scale-Out NAS. I demand they change the acronym to Seriously Ossum NAS. It’s a brilliant design in its overall simplicity, combined with absolutely ridiculous density. If anyone’s going to get this right, it’s not Sun – I mean Oracle, it’s going to be IBM. They have the budget and resources. And SONAS delivers, if the order is NAS. I am a little dubious of some aspects of SONAS, but these are software issues and not hardware issues. Software issues should be able to be fixed without needing to forklift the hardware.

What software issues am I concerned about? SONAS is going up against not just Oracle, but NetApp, EMC, HP, Dell and so on inevitably. In that regard, it’s lacking in the snapshot to application integration NetApp and others have. At the price points IBM’s talking on SONAS? Integrating with applications for snapshots is pretty much expected. There are a lot of other software integration and capability questions that IBM has so far left unanswered (without NDA,) so it’s very much a wait and see. The hardware has the potential, it’s up to the software to execute. But at least they’ve solved the back end portion already with GPFS.

The good while being less than brilliant; “VDS.” This ‘offering’ is almost insulting to the capabilities of the IBM SVC. The VDS product cripples the SVC by chaining it to IBM’s low and midrange storage, the DS3k and DS5k. Look, you’re not likely to sell any business who’s had a DS5k another DS5k. The architecture is positively ancient, and is still incapable of anything beyond the most basic of maintenance being performed online. Any firmware maintenance absolutely requires hours of downtime. The DS3k doesn’t even attempt to fake online maintenance capabilities – it just can’t, and it’s not meant to.

But this is a channel play. Why? Beats me – IBM could certainly use more solutions as opposed to just products. My opinion is that it would be a lot smarter to keep VDS close to the chest, and offer it with DS3k, DS5k and DS8k. Seriously folks, the DS3k and DS5k can produce great performance numbers, but they have not been and will not be true enterprise arrays. You have a minimum 2 hours of downtime per year – that’s minimum, not typical – for mandatory firmware upgrades. Why? DS3k and DS5k require stopping all IO to do controller, ESM and disk firmware. So the SVC’s high availability ends up somewhat wasted here. Only the DS8k is on par with the SVC for high availability while servicing.

And the patently ridiculous and arguably false, otherwise known as codifying stupidity. I’m going to give you a quote, and you’re not going to believe it, but it’s a very real quote.

"XIV can reach up quite a long way and run parallel to the DS8000.” –Steve Legg, IBM UK Storage CTO

Yes, that’s Steve Legg of IBM UK saying that the XIV is the equal to the DS8000. Now Steve, the horse is out of the barn, and you can damn well believe I’m going to call IBM out on this load of manure. That statement has absolutely no basis in fact by IBM's own published case studies and reference sites, and even a cursory review of specifications between the two arrays reveal it to be obviously disingenuous at best.

But let’s have a refresher of those spec sheet contents, shall we?

XIV is comprised of 15 modules totaling 180 1TB 7200RPM SATA disks with 120GB of cache and over 7kAVA of power draw at idle and a peak of 8.5kAVA at 29000BTU/hr. The only RAID type is mirroring, reducing actual capacity to 79TB before snapshot – this is also the maximum capacity of the XIV, 79TB – it is not possible to span frames except to mirror them. You cannot grow past 79TB and there is no intent to move to 2TB disks in the next generation XIV hardware. Disk interface is 12xSATA over Gigabit Ethernet, changing to SATA over InfiniBand in the next hardware release (forklift upgrade required.) Protocols spoken are Fiber Channel 1/2/4Gbit and iSCSI over Gigabit Ethernet with a maximum number of 24 FC ports and 6 iSCSI ports, with host ports removed for Mirroring HA (the only HA method available.) Major component maintenance is limited and customers may perform absolutely no service on XIV whatsoever. And I do mean NONE; even a simple disk replacement must be performed by a specially trained CE. IBM shipped the 1000^th XIV in November of 2009.

DS8000 is now four generations old, comprised of the DS8100, DS8300, DS8300 Turbo and recently introduced DS8700. Based on the IBM POWER architecture as a controller and using custom ASICs, the DS8000 family doesn’t just hold but absolutely owns the SPC1 and SPC2 benchmarks. Two processor complexes provide from 32GB to 384GB of combined cache and NVS. The DS8700 ranges from 16 to 1024 disks using any combination of 73/146GB SSD, 146/300/450GB 15K RPM, and 1TB 7200RPM disks in packs of four or sixteen with a maximum capacity of 1024TB. RAID levels supported are 5, 6 and 10. Disk interface is FC-AL via multiple GX2 connected IO Complexes. The frame ranges from a single wide cabinet to 5 frames (base plus four expansions) with minimum power draw of 3.9kAVA base, 2.2kAVA per expansion and maximum of 7.8kAVA and 6.5kAVA respectively. The thermal min/max is 13400/26500BTU/hr and 7540/22200BTU/hr respectively. Protocols spoken are Fiber Channel 1/2/4Gbit and FICON 4Gbit with a maximum host port count of 128 in any combination of FC and FICON. Almost all major component maintenance can be performed without needing to shut down the DS8000, and all prior models can be field upgraded to the current DS8700 941/94E. Customers may opt to perform most DS8000 maintenance tasks themselves and some hardware repair, including disk replacement.

As you can see, these two systems are not even remotely similar or comparable. The absolute maximum disk IOPS an XIV is capable of, being as generous as we can be at 180 IOPS per disk, is 32,400 IOPS. The DS8700 using FC disks and the same 180 IOPS per disk as a conservative number, is capable of 184,320 IOPS. This is ignoring all buffering, caching and advanced queuing. The DS8700 is proven to be capable of well over 200,000 IOPS with a high number of hosts. IBM refuses to submit XIV to an audited benchmark and their most detailed case study with Gerber Scientific shows XIV only handling a total of 6 systems (claiming 26 LPARs, that's still ridiculously tiny) and using less than 50% of its available capacity.

For IBM to even insinuate that the XIV is “parallel” to even the DS8100 first generation hardware is to basically call their customers idiots; it is the same as telling MotorTrend that your 1985 Yugo 45 can keep pace with a 2004 Ferrari Enzo. It’s only true as long as they’re both doing 25MPH and you’re willfully ignoring everything other than the fact that they both can do 25MPH. Anybody who spends more than 10 seconds reviewing the specification sheets for these two systems or cars will immediately be able to tell that they are not in the same class. Yet IBM would very much like you to believe that their Yugo 45 is just as fast as their Ferrari Enzo. Perhaps a more apt comparison would be that Steve is currently telling you that IBM's Renault Twingo can totally hold at least as many people as their London Double Decker Bus.

Am I calling Steve Legg an idiot? Absolutely not. Steve just made an amazingly bad word choice. Steve Legg is a well respected guy, and not someone who's going to call you daft, especially not customers. But he’s basically said that IBM’s organizational stance is that customers aren't smart enough to spend a few moments reviewing a spec sheet, and seeing the obvious disparity between the two arrays. He’s saying that IBM believes customers are too stupid to see the inefficiency of the XIV as compared to its “green” claims, too stupid to see the raw horsepower of the DS8700, too stupid to tell the difference between 7200RPM and 15000RPM, too stupid to understand that 3.9+2.2/7.8+6.5 kAVA is more efficient than 7+7/8.5+8.5 kAVA. The problem with this is that the special XIV people will latch onto these words, yet again, and continue to use them while they do treat customers like idiots. (Those who claim they don't, I had them telling me to my face that the numbers they were putting up on the screen as gospel, didn't mean anything. Among other things.)

Yet again, this does not mean XIV does not meet some needs. What it does mean is that XIV is still not equal to nor does it offer performance comparable to the DS8000. 

His statements show that IBM’s offerings have codified stupidity; “we now sell on the basis that customers are too stupid to read or question us.” When customers push back on the high cost of DS8000, just whip out the significantly cheaper and far less capable XIV without mentioning anything other than "it can run parallel to the DS8000!" Which only goes to further support my arguments that you should be questioning your vendor at length, demanding hands on testing, and refusing to take their word for it on any statements of suitability or performance. The choice is yours – you can challenge your vendor, or you can enjoy the challenge of finding new employment. And you should be really extra careful about what exactly you say to the press, especially when you have a fiefdom that doesn't answer to you itching to abuse it.

Update:
I'm sorry about the VERY poor wording on my own part, and I want to extend my sincerest apologies to Steve Legg if I caused any offense. (I should not be writing so late, obviously.) Steve is by all accounts a great guy, and I'm sure that it wasn't his intent to imply that customers are idiots. The problem is that he made a bad choice of words and phrasing, and that's how it came out. I'm quite positive he knows better, especially since IBM UK is the home of the SVC.
The problem is that's how the words went and how the offerings are now aligned, and what it says to me as a customer. But they're also not decisions that are made by just one person at IBM, and Steve is just the messenger in this case. He certainly isn't deserving of, and I certainly would not rain my wrath down upon Steve specifically. If you ever get a chance to meet Steve Legg, be sure to shake his hand and thank him for SVC. ;)

Flat Tiering - it doesn't suck, it's just your configuration that sucks.

I hear so much anti-flat-tiering noise lately, it's past time I spit out my thoughts on it.
First, what is flat tiering? That's any storage system where you have one or two types of disk, and that's it. Some examples would be the Compellent, Pillar Data Systems, Data Domain Networks, and 3par T and F series. All of these systems use one or two disk types in the system, and that's it. Why is this a good thing? One, it reduces servicing complexity - you don't have to identify which type of disk or controller needs replaced, because they're all the same. Point two goes back to the subject above - configured right, there's no reason to mechanically tier everything.
Flat tiering is not one-size-fits-all. It is not right for every configuration. It is not right for every application mix. But it fits most setups well - when it's configured correctly.

Certainly, this is far from specific to flat tiering. Do not ask how many badly configured mechanically tiered setups I've seen. Bad configurations are more common than people want to admit. Usually it's holdover configurations from initial deployments done in a rush, where there's too much loading or not enough spare resources to perform a reconfiguration on. Either way, bad configurations are bad configurations wherever they are.

Here's the thing with flat tiering though - when your configuration sucks, you REALLY know it. It's not like a DS5k where your bad configuration only pushes your response times up to around 20ms, or an SVC where you reduce theoretical peak throughput by 50% (which still gives you about 4.5GB/sec.) A bad configuration on a flat tiered system can push your response times over 50ms and drop your IOPS through the floor. And it's much easier to badly configure a flat tiered system than a mechanically tiered system.

The first thing you have to do, and I really do mean have to do when you work with a flat tiering system is throw everything you know about configuring mechanically tiered systems away. Forget all of it. It's only going to wreck your configuration. The second thing you have to do is document and test more first. I don't mean figure out what needs high priority and how many terabytes it needs - I mean really document and test. What's your typical IOPS for this application? What's your maximum acceptable response time? Is this random disk seeks or sequential loading?
Let's look at mechanical tiering. Basically, it goes something like this: if it has to be fast, put it on fast disk. If it can be slow, put it on slower disk. If it can be really slow and it's mostly sequential, put it on SATA. Flat tiering does away with all of that. Every last bit. There is no fast and slow disk, there is just disk.
This is where the biggest mistakes happen. People assume that this means they simply shift their entire design philosophy to capacity and nothing else. Capacity becomes the commodity and all performance is equal.

Can I get a show of hands from 3par, Compellent, DDN, and Xiotech who agree that flat tiering means capacity is the sole concern of their product, and all performance for all LUNs presented to hosts will always be 100% equal at all times?
Huh. I didn't see any hands there. Maybe I didn't ask loud enough? Or maybe that's because it's just not true. While performance across all LUNs on most of these systems will tend towards equal that does not mean it is equal, or should be equal on all LUNs.

Think about it. Do you want your PeopleSoft database to have the same access priority as your customer service file shares? Of course not. That's just silly. You need that PeopleSoft database to be on the fastest possible disk you can get. But you're on a flat tiered system, so you don't have faster disk. And there's only one product where 'flat disk' means 'flat performance' - and I won't even mention which, because it's just a bad storage system period. Ask any of the vendors I've mentioned above if flat disk means flat performance, and they'll tell you bluntly "no." It does tend toward flatter performance, but that isn't the

This comes back to the point of better documentation and understanding of storage requirements. If you attempt to treat all storage as equal, you are much more likely to get burned. A performance hit to your Windows shares becomes a performance hit to your ERP systems. Obviously this is the last thing you want to have happen in your production environments. That's why there needs to be greater focus on the storage, and a greater attention to detail. Storage complexity doesn't reduce, it just moves. You need to have a greater attention to detail than you're used to.
Nor can you just apply traditional best practices. They don't apply here. With different RAID modes, different technologies, and different methodologies of achieving storage performance, simply going with what you're used to isn't an option. You can't just throw together 4+1 RAID5's and call it done. You need to look at how each system does RAID, and how it applies to performance from the host perspective. You can't just throw more spindles at a slow database - it may even further hurt performance. You may need to increase controller priority, or adjust how the arrays are caching.

The other thing I see is a stiff resistance to SATA in traditionally FC spaces. This is right and wrong. Whenever any vendor is trying to sell you SATA instead of FC, you should be extra critical. That doesn't mean throw it out. That means you test, test, and test again. You test on real hardware with loads as close to real as you can get. You don't buy a thing until they prove every single claim. The fact is that SATA sucks for random, period. Every single vendor I've named knows and acknowledges this - that's why they all offer FC or SAS drives and SATA drives. If the salesperson is trying to push you to go ALL SATA, chances are they don't know what the hell they're talking about, or they see something in your workloads that you missed. Understanding your workloads is something you need to do before you even start talking to sales.

Flat doesn't necessarily mean really flat. Sometimes it means replacing 6 controllers and 32 arrays of FC disks with one or two controllers with far less arrays, achieving equal or greater performance. It does not need to mean limiting yourself to a single disk type or speed.
And let's go back to making them prove their claims. 3par can brag about some of the best SPC-1 results around, the F400 pulled off 93K IOPS with a respectable response time. That's a great demonstration of what their technology can do, using 146GB 15K FC disks. It is not a demonstration of what it will do in the configuration they're selling you. Your workloads might push their controllers harder than they expect. Your workloads may be poorly suited to the disks they're suggesting. Test, test, and test again. Make them back up their promises in writing. That's true of all storage, sure, but doubly so in this space.

The thing is, I know for an absolute fact that at least two vendors I've named in here (no, I can't say who) have backed up their claims of offering better performance and reliability in writing, in full. I know this because one, I was involved directly or peripherally in it, and two, they made good on those promises. I seriously can't say who, because it is NDA'd and proprietary information regarding customer agreements.
But I will tell you right here, right now, that if you ask any one of the vendors listed above to back up their performance and reliability claims in writing, with a guarantee to cover costs of removing them or going back to your existing storage there are two who can and will look you right in the eye, say they can do it, and will put it down in writing. And the requirement that you test, and work with support to achieve it? If that isn't standard operating procedure for you on traditional arrays, you need to reexamine your SOPs. (Again, test test test! You cannot test enough!) Anybody who won't back up their claims in writing, either shouldn't be making claims, or should be axed from your shopping list fast.

Oh, and that flat array I won't mention? IBM XIV. My recommendation? Don't even touch that thing. It is dangerous, and not ONE of the claims I have heard from sales in the past is true. IBM's own presentations show that XIV can barely beat the DS3400 in random IOPS and can't even match the DS3400's response times. XIV is complete crap for anything that isn't purely sequential read with <40% write and <20% random. If that isn't true, why hasn't IBM backed their claims on XIV with SPC results? DS3400 has 'em, DS5300 has 'em, XIV still doesn't over two years after it's introduction.

The Protocol Wars Continue.

http://viewyonder.com/2009/11/12/the-end-is-nigh-for-protocol-passionistas/
Hey guys. My turn.

A lot of the Protocol Passionistas are arguing for all the wrong reasons, absolutely agreed. Some folks probably lump me in there, because I am resolutely against FCoE at this point in time. But not because I like having to run MTP and pinch my fingers in high density cassettes. And not because I hate Ethernet. Oh, and also not because I'm against FCoE either.

The problem I have with FCoE, is the problem I had with NDMP, with iSCSI, with NFS, with any number of protocols. People like to jump the gun and don't pay enough attention to best practices or the limitations of the protocol. FCoE has great potential for good, but far more potential for bad. Think about it for a minute. Can you honestly say you have never seen a poorly configured SAN or Ethernet switch, not once in your entire career? If you said no, you probably haven't been looking. I actively seek those problems, to solve them before they become real problems.

Now let's apply this to converged networking, where we now have FC (disk and tape,) iSCSI (slower disk,) and Ethernet (networking and NAS,) all carried on the same fiber through the same adapter. The Reliable Ethernet part of the stack was only very recently declared tech stable, and is without question the most critical element for FCoE. Buying into things before you know you won't have to forklift for the final standard, not wise. It's important to point out that none of the protocols involved are spring chickens. Even iSCSI is years old. And compared to it's age, real stability is very recent.
And now, we're shifting all of these onto a single converged point. What this means for business is the Elephant in the Room that nobody, and I mean absolutely nobody, wants to admit to. Networking failures and problems, just became everything problems. This isn't a Protocol Passionista point - it's a point period. And a very good and valid one. Lumping all your eggs into one basket, even with redundancy, can be very dangerous. Remember what I said about configuration problems before?

Jumping into the new challenge of converged networking, without meeting the challenge of current networking is such a bad idea, I can't recommend it. And it's still relatively young, giving me additional pause. There is tremendous risk of making mistakes, and mistakes cost real money. Especially when a failed Ethernet port now means failed disk as well.

No question, converged is the future. Like it or not though, the reason isn't what people want it to be. It's not because it's technically superior, it's not because the old division of protocols is a bad idea.
Converged is the future because it's cheaper.
Yes, that's really what's going to drive adoption. The folks controlling budgets saying "why do you need two $1200 HBAs and two $400 multiport GigE cards when the salesman says we can do it with a single $1100 converged adapter?" Ask any budget decision maker - will they take a proven reliable method when there's something significantly cheaper that's 'good enough'?

And once again, it will fall to us to turn 'good enough' into "we can't ever be down unexpectedly ever."

On Virtualizing your Storage

Way back, I went over what's virtualization on Unix, and what's not. Well now it's time to hit storage over the head with the debunking hammer!

So, let's start with defining virtualization in the storage context. Storage virtualization is taking a homogenous or heterogenous set of storage resources, and distributing data over multiple arrays or controllers. That's the simplified version. There's a complicated set of requirements to actually qualify as storage virtualization. I'll break it down in a list format.

• It must support more than one controller and more than one storage subsystem.
• It must support more than one vendor's storage subsystem(s).
• It must support more than one model of storage subsystem.
• It must support at least one protocol of: Fiber Channel, iSCSI, or NAS.
• It may or may not include it's own disk storage controllers.
• Data must be capable of being spanned across two or more attached storage subsystems while being presented to hosts as a single LUN.

So we've got a good list of what is required to qualify, in my world, as storage virtualization. So, let's do the list! What IS Storage Virtualization? (In reverse alphabetical order, and not a complete list.)

Actually Virtualization

• NetApp V-Series
• LSI StoreAge SVM
• IBM System Storage SAN Volume Controller
• Hitachi Data Systems USP-V
• Hitachi Data Systems USP-VM

Definitely Not Virtualization

• HP LeftHand P4000 - scale-out is not virtualization!
• EMC V-Max - does not attach to ANY other vendor or controller.
• EMC Invista - does not support to ANY vendor except EMC.
• Coraid ATA-over-Ethernet products - single vendor chassis with storage built in!

Don't Know Enough, So Might Be!

• Incipient Network Storage Platform
  They hide all their documentation and technical specifications, so I can't tell if it's just a tool for mirroring and copying between different storage subsystems or it's actually virtualizing.

All that said, there's the argument that could be made that if the product hides the storage behind it and presents a single point of management for your storage, then it's virtualization. But, it's not. It's a gateway.
The EMC people will whine about V-Max being defined as "Not Virtualization." TOUGH LUCK. IT ISN'T. The V-Max is a storage subsystem, which spans data across multiple arrays and multiple controllers within itself. The V-Max does NOT support any externally attached arrays from any other vendors. The people who want to whine about Invista? TOUGH LUCK. IT STILL ISN'T. The Invista slid into supported EMC array cabinets and only worked with EMC.
It's NOT virtualization if it only works with one storage vendor. Period. The point of storage virtualization is to enable heterogenous environments. Be it tiering by applications, saving money by using multiple vendors, or increasing performance by using multiple arrays and subsystems.

So why would you virtualize your storage? There's dozens of good reasons. The one I hear the most frequently is the IBM SVC owning SPC benchmarks. They want that level of performance out of their storage, and they think virtualization is a magic wand. It isn't. Virtualization is, like all things, a piece of the puzzle. No more, no less. Can you rock your world with SPC record breaking performance by going to virtualization? Sure, if you pay for it. Just like everything else.
Virtualization is still a front end to storage subsystems. That means that just because the virtualization engine can do 9,500MB/s random, you're still limited by the arrays behind it. The counteracting component is the use of multiple controllers and arrays. One array does 250MB/s random, but with virtualization you can span the LUN across two, which gets you to 500MB/s random in theory. In reality, it'd likely be closer to 400MB/s, but that's still way up from 250MB/s. Need more performance? Add more controllers. It doesn't hold 100% true, and there's a scaling point where it stops helping, but that's the theory.
From the administration side, virtualization is very appealing. This is also how many gateways claim to be virtualization. A key tenet of storage virtualization is that it must provide a single point of management for your storage, regardless of what's behind it. When you virtualize, all your disk to host provisioning is done in the virtualization engine. You no longer need to slice things out on each controller after looking at loads, what space you have, etcetera. It consolidates the vast majority of your storage management into a single pane of glass.
So far, we've established that virtualization can turn multiple low-performance arrays into solid performing LUNs for your hosts, and your administration nightmares can be drastically reduced.

Now I'm going to tell you why both of those are bad too. First, administration nightmares only go down if you're capable of configuring things that way. You have to be ready to let go of individual arrays for individual applications on your storage subsystem. You create a bunch of large, high performance arrays and give them to the storage virtualization engine to manage. It writes blocks across those arrays. Stop managing spindles, start managing performance. Group arrays by performance and by capacity in your storage subsystem, not by application. Group by application in your storage virtualization engine.

Low performance arrays are STILL low performance arrays. If your issue is seek performance, virtualization will not help you. Seek performance is dependent on the arrays behind the virtualization layer, and the virtualization adds seek penalty - anywhere from 40us to 5ms depending. Putting two SATA arrays behind an SVC will not get you FC. It will get you 1.5 times SATA. Virtualization is not a replacement or workaround for baseline array performance. It's a way to enhance performance. And the most common configuration error? People tier their storage by controller. Tier 1 is this storage subsystem, tier 2 is that storage subsystem, and tier 3 is yet another. You won't realize significant performance increases from this configuration. You'll dramatically increase spindle count, but you become hard limited by controller performance, and unbalance controller loading. The optimal configuration is to span tiers across multiple controllers. 3 Controllers with 10 arrays of 5 SAS15k disks, 10 arrays of 5 SAS10k disks and 10 arrays of 5 SATA disks will typically perform better than 1 controller with 30 arrays of each type of disk. The load becomes more balanced across all three controllers, rather than having one controller sitting idle while one is begging for mercy.

So, how do you determine if virtualization is right for you? If you said "I have more than two storage subsystems and I need better performance and ease of management," I want that gold star back right now. First and foremost, storage virtualization is not for everyone, it's not always appropriate, and it's not a cheap solution to an expensive problem. Storage virtualization allows you to consolidate multiple heterogenous resources into a single point of management and allocation. That's it. Performance benefits should not be at the top of your list of reasons. Does that mean it can't be? No, but it shouldn't be the primary reason you're taking your first looks at storage virtualization, or even your second looks. Many environments can realize performance gains for far less money by analyzing and optimizing their storage configuration to suit their environment. And no, I don't mean best practices. Best practices are a starting point - not an end point. Reconfiguration of existing storage might buy a lot more than you expect.

Storage Virtualization fits most easily in rapidly or frequently changing environments, medium to large environments looking for increased scalability or flexibility on existing or new hardware, or environments with large amounts of administrative overhead. I'll get shot for saying it, but I'm going to anyways - in some environments, storage virtualization can change the staffing requirement from 5 to just 2 or even 1 Storage Admin. That doesn't mean it isn't suited to other environments, just that these environments are the most likely to receive immediate benefit from storage virtualization.
Unlike server virtualization and partitioning, storage virtualization is still rather immature. If a vendor starts telling you they solve everything including the kitchen sink, be wary. Every business should look at the costs and benefits of storage virtualization on a case by case basis, with detailed analysis not just from the vendor, but from internal staff as well. Can you use your existing storage subsystems? Can you expand with new subsystems? Will you have to forklift upgrade the storage behind it to expand further? Does it support your preferred vendors? Who's using it for what application with what results?

Storage virtualization has amazing potential in many, many environments but it also has the capability to burn you just as badly.

Come back later, where I openly mock every VTL on the market for being the utter crap they are courtesy of an obscure company with an unpronouncable name, and complacency on the part of manufacturers!

Storage - What IS non-disruptive?

This grows out of a discussion going on over here:
http://wikibon.org/blog/migrating-data-within-federated-storage/

The two main systems up for discussion here, are the IBM SVC 2145 and the Hitachi Data Systems USP-V class. So, let's start with some background on the systems.
The IBM SVC 2145 is like most IBM products, an amalgamam of acronyms. The official name is the IBM System Storage SAN Volume Controller. The SVC is a Storage Virtualization Engine, presenting hosts with a unified front-end, SAN Admins with a single point of management, and utilizing any number of disk controllers behind it. It is also the current (and probably forever) record holder of just about every SPC benchmark and a large number of TPC benchmarks. The currently available (and not the announced) hardware offers from 8 to 32 4Gbit FC ports per cluster, as many disks as you can fit into 4,096 MDisks as of 4.2.1 - using RAID5 in 4+P that's 16,384 spindles! Maximum actual spanning is limited to 512 spindles for a single VDisk, which is still jaw-dropping.
The Hitachi USP-V is a beast. A lovely, lovely beast I want for my very own at home (except for the power bills.) It doesn't hold a lot of records because not enough people show it love, in my opinion. The latest generation offers up to 1,152 drives in 1-4 expansion frames with up to 128 flash drives, 512GB of cache, and up to 224 Fiber Channel ports. Everyone else, eat your hearts out. The USP-V also includes all of Hitachi's fancy software offerings, and the ability to assume control of and pseudo-virtualize external storage arrays like IBM DS4000's, HDS AMS-series, and so on.

If you just went "wait, these sound like very different products" that's because they are. You see, the IBM SVC is a Storage Virtualization Engine and the HDS USP-V has a Storage Virtualization Engine. But the SVC offers no storage disks of it's own whereas on the HDS USP-V being disk storage is the core functionality. In other words, we're comparing something with no disks to something that's built entirely around disks. Vendors are getting very good at blurring these lines very badly, or explaining their products very vaguely, resulting in some pretty bad customer confusion.

So which is which and what is what? Let's start with the IBM SVC. The IBM SVC is two to eight 1U systems in an appliance form, which you stick in front of supported disk controllers to provide extent-based virtualization (or not) and/or provide you with a single point of management and presentation for a variety of hosts. Connections to hosts and storage are via standard Fiber Channel, and cluster interconnect uses standard Gigabit Ethernet. The SVC also offers the advantage of using IBM's SDD multipath driver which is available for every major OS out there in driver or pluggable software module form.
This brings us to the HDS USP-V. The HDS USP-V is a high end enterprise storage system boasting some of the most impressive specs you can find. It's highly configurable and customizable. It offers gobs of high speed SAS disks as well as support for SATA disks using HDS' RAID1+, RAID5 and RAID6 algorithms. Like the IBM DS8000's, disks go in 4 at a time at the minimum. The internals are connected via Hitachi's proprietary (not in a bad way) Universal Star Network. External storage is attached via Fiber Channel.
(As a note; I'm not including iSCSI because it's only an announced feature on the SVC, and NAS is the realm of the USP, not the USP-V. Plus we're not comparing features, dangit!)

Now if you read the original post on Wikibon that started us down this road, you'll notice that it was about what constitutes non-disruptive block level virtualization. (Or extents, if you want. Pick your poison.) Some folks have said that only the USP-V does it. But, that's not true. You see, the SVC also does everything the USP-V does. So what's going on here? Well, there's two problems.
One, the USP-V is storage with virtualization while the SVC is just virtualization. Two, the definition of non-disruptive is.. ambiguous at best, tenuous at other times, and just crazy at still others.
Let's start with my definition of non-disruptive. My definition of non-disruptive is being able to perform hardware repairs, software upgrades and hardware upgrades without impacting the production environment beyond performance. Most folks will tell you that my definition is pretty darn reasonable.
HDS and IBM like to redefine "non-disruptive" on a per-product basis, to suit their needs. It's marketing, don't pretend to be surprised, okay? This is what they are paid to do.
So, if we go by my definition, why do both of these systems offer you the potential of non-disruptive maintenance and upgrades? Because they both do. And the SVC may even slightly edge out the USP-V in this regard because of it's appliance nature. (I'll explain, I promise!)

The caveat that both systems are subject to is the actual storage subsystem and attached hosts. Yes. The disks and the end consumers of LUNs. The USP-V can legitimately make that claim because without adding external storage, it's still a USP, offering non-disruptive firmware upgrades and hardware replacement within practical limits.
The SVC can also legitimately claim to be non-disruptive block-level virtualization too. Why? Because the SVC itself can do everything HDS claims to be do non-disruptively as well. Data migration between arrays, between nodes (IO Groups, in fact,) and even between clusters. All that it requires is that the storage subsystems behind it be able to do firmware and hardware maintenance non-disruptively.

This is also where their claims fall apart. For our example, we'll be using the venerable LSI designed-and-built IBM DS4800 storage controller and EXP810 shelves. For the record, I hate the DS4k/DS5k because it is absolute crap for enterprise storage. But it's cheap so it's everywhere. It's still crap.
Given the DS4800 as an External Storage Array on the USP-V and the SVC, both solutions fail the non-disruptive claims. Even the ones their own manufacturers make. Why? Because it's a DS4800, and they're both dependent on it. Firmware upgrades on the DS4800 are fraught with terror and most decidedly disruptive, requiring all IO be stopped to the DS4k. That means any arrays with data on the DS4k must have IO stopped at the virtualizing layer before maintenance can be performed. Which means stopping them at the USP-V or the SVC. Which means shutting down production environments using those LUNs. Was that a "whoops" I just heard?
But by the same token, if we take a USP-V with an AMS2500 behind it, and an SVC with an AMS2500 behind it, both pass because maintenance on the AMS2500 is non-disruptive. See how it works? Now you can dislike marketing crap just as much as I do!
However, within the isolated products themselves - that being the USP-V and only the SVC (with no storage,) all tasks are non-disruptive. As of 4.3.x you can take an SVC from 2145-4F2 hardware to 2145-8G4 hardware in the middle of the day with no impact to your production environment beyond performance, with proper planning.
So why does the SVC slightly edge out the USP-V in non-disruptive? Because the SVC is an appliance you put in a standard rack. If you put each IO Group (two nodes) in separate racks, which you should, the SVC can continue to operate normally through physical moves - excepting when managed storage is shut down for moves. The USP-V can't, because the controller is in a single dedicated frame. Yep. That's the entirety of it.

What about host side? HDS claims to be unique in their ability to migrate a disk non-disruptively between USP-V frames. Well, one, the SVC can do this with Metro mirroring (not to be confused with Global mirroring! Global is the one for long distances!) or within a cluster using VDisk mirroring or FlashCopy (which HDS has equivalents for for in-frame, predictably!) Two, apply brakes when the reality of hosts hits.
No, Virginia, there isn't any such thing as a free lunch and migration between frames or between clusters will always, always be disruptive at the host level. You're changing WWNNs and WWPNs on the controllers, even if the rest isn't changing. And you think a host will just smile and eat it? Boy, don't I wish - that would save me SO much trouble, both past and present! No, no. The hosts will get very, very upset with you. So what's the procedure?
Well, I can't speak to the USP-V's since I haven't done it. But I imagine it's somewhat like the SVC's with obvious key differences. The USP-V is doing a migration from Frame A to Frame B. The SVC is mirroring data between Cluster A and Cluster B. To complete the migration on SVC? You unmount the disks at the host. Reverse the mirror direction. Rediscover disks on the host. Mount the disks from Cluster B. Verify everything is happy, and break the mirror. 5-15 minutes of downtime, typically. My guess is that the USP-V is similar in needing to stop IO and unmount, start migration, rediscover disks to pick up the new frame's ownership, and remount while migration is in progress. In theory, this could be fixed in software, but it's a very difficult problem to fix.

So, what've we learned today? One, don't take the vendor's definition of non-disruptive at face value. Ever. Two, do your own homework and don't just settle for "magic quadrants" and glossies. Insist on tech demos that don't simply consist of the vendor demonstrating the feature on a cherry picked array. Insist on hands on time. Insist on talking to real customers.
This post is a great example of exactly why you should. I learned about things the USP-V can do inter-frame that I didn't know before. And hopefully people learned about things the SVC can do that IBM marketing didn't tell them. (Seriously, IBM marketing sucks.)

And I can hope everybody learned a bit about the practical limitations of any storage virtualization solution, be it HDS, IBM, EMC or Joe's Computer Shack.

Aaaaaand the disclaimer!
I don't work for IBM, Hitachi, any subsidiaries, VARs, or BFFs. Despite my lust for the combination of SVC + 2x AMS-2500 in my home, both IBM and HDS have failed to ship me either, or even so much as a cheap mug! I hope you guys are listening, 'cause I could use a new mug after my Sun Customer Appreciation mug broke. ;)