Storage virtualization technology pros and cons

Our podcast outlines pros and cons of storage virtualization technology, as well as how to choose between file-based and block-based storage virtualization.

Storage virtualization technology can be a big help to data storage managers. Storage virtualization technology reduces the amount of physical storage by pooling multiple devices together to make it look like they're one storage device that's controlled at a central console. This simplifies backup, recovery and other storage tasks, as well as the time it takes to do them.

But storage virtualization technology has its challenges. Storage virtualization software and hardware are often offered by different vendors, which can make it difficult to solve problems when something goes wrong.

In this podcast, Marc Staimer, president at Beaverton, Ore.-based Dragon Slayer Consulting, discusses storage virtualization technology. Find out the pros and cons of storage virtualization, when to rule out storage virtualization in your environment, and how to decide whether file-based or block-based storage virtualization makes sense in your shop. Read his answers below or download the MP3.

Listen to the storage virtualization technology Q&A. What are the main benefits of storage virtualization software for storage managers?

Staimer: Storage virtualization software is different than server virtualization software, so the benefits are different. And to understand the benefits we need to look at the differences first. When you use storage virtualization software what you're doing is converting a server, typically an X86 server, into a storage controller. Now you can turn that controller or server into the controller, and the storage inside the server into the storage system. Or, typically, you can use storage outside that server as part of the storage system.

Server virtualization takes a server platform and makes it appear to be multiple platforms by virtualizing the hardware and giving you access to it from multiple operating systems and applications, so it's a different approach. The real benefit of storage virtualization is that you can use commodity hardware or less-expensive storage to provide enterprise-class functionality.


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Storage virtualization technology benefits and drawbacks

Storage virtualization services Looking at the other side of storage virtualization, what are the chief challenges users seem to be running into?

Staimer: The biggest challenge of storage virtualization is that you end up with multiple vendors. Storage has traditionally been a very risk-adverse market -- risk adverse meaning that people don't really want to take a lot of chances -- and this is because you don't want to lose your data. As a result, many organizations would prefer to buy from a vendor that provides them with a complete storage system. If there's a problem with the software, it's one vendor [to deal with]. Storage virtualization software means you're buying the software from one vendor and typically buying the hardware from another. So when problems occur you have to be pretty technically astute to solve the problems and isolate whose problem it really is. Are there certain circumstances or environments where you should avoid storage virtualization technology?

Staimer: It depends. Right now storage virtualization is showing up in every storage system. If you see the concept of the virtual LUN or virtual pool of storage, there's storage virtualization in there. If you can move data from one volume to another without being disrupted, that's a form of storage virtualization. Thin provisioning is a form of storage virtualization. So the question that makes more sense is: Is there a situation where you should avoid storage virtualization software that's separate from hardware? Yes. If you're worried about the finger pointing that goes on with vendors that could be a big reason. Many vendors on the storage system side will avoid their warranty if they're behind someone else's storage virtualization.

Now that's more true in the block storage side than the file storage side. File storage virtualization is a little bit different because you can do virtualization without actually controlling or being in the pass of the data, and you can do that a lot more effectively than you can with block. Let's say you want to determine whether block-based storage virtualization or file-based storage virtualization is right for you. How should you go about doing that?

Staimer: Well, first, are you a file shop? Are you a NAS shop? Is that your primary storage or is that the area you're trying to grow? Is that where you're having most of your problems? It's not really a matter of which one is right for you, but rather which one you're using at any given time. If you're using NAS, if you're using block storage or SAN storage, odds are you're using both. So where are your issues? If your issues are on the file side, I would suggest file virtualization is a good play, and depending if it's Microsoft or NFS, that would depend on which vendor you go with.

On the block side it's a little different. If you have SAN storage and a taste for being more in control of your environment and how it works and interoperates and integrates, you want to control the hardware and software, and you don't mind different vendors, then it's a good play if it solves problems for you; and there are a lot of problems it solves in both file and SAN storage. Who is leading the way in storage virtualization technology?

Staimer: That's a very difficult question because storage virtualization is so broad and typically it's different than server virtualization in one other key factor -- it's not really a separate market segment. With server virtualization, you see that as a complete and separate market segment because it takes control of the server hardware and divvies it out to the operating systems. So the operating systems no longer control the hardware. In storage, you tend to find that it's been morphed and migrated. The whole virtualization functionality is moved into the controller, so every storage vendor has their own storage virtualization.

Having said that, I have to say that EMC is one of the leaders; NetApp is one of the leaders; Hitachi Data Systems is one of the leaders. Even IBM is one of the leaders. And depending on how you measure it, IBM will claim they're the leader because they've sold more SVCs than anybody. SVC is their SAN Volume Controller, which is their virtualization engine. They've now migrated that functionality into a storage system they call the Storwize V7000. So as you look at what everybody's doing in the space, it's virtualization, and with some it's more advanced than others. For example, Hewlett-Packard 3PAR is an advanced form of virtualization, but then you move into other aspects of virtualization on the NAS side. And the most advanced on the NAS side is Avere Systems. They're providing a scale-out clustered appliance that isn't in the path of the data, ultimately, if you lose the appliance. But if you want performance, it is. It's a very interesting hybrid approach.

There are others that do a great job with virtualization. Almost all scale-out NAS is a variation of virtualization, and I can list dozens of scale-out NAS players at this point. Object-based storage is a variation of virtualization. So the better question to ask is: Who's solving the most problems well? And that's a different animal altogether. I could look at performance and cost performance problems; then I could say a company like Xiotech or Nimbus Data solves problems very well -- they're both using a variation of virtualization. I could say EMC solves a much broader slew [of issues] because they have a broader portfolio, but individual problems? Maybe not as well, but in some cases better; it just depends. I can look at NetApp, and it has a broad portfolio and they solve some problems really well and others not so well. So it's a tough question no matter how you phrase it. We saw such a surge in server virtualization technology; how does storage virtualization compare? Where are we in the adoption cycle?

Staimer: I would say server virtualization is a complete and total separate market segment. It's a technology in which it's looked on, dealt with, implemented as a separate and complete function inside of the data center. Storage virtualization is a feature of storage. You're not going to see the same things that way. Ultimately, it does not have, in the eyes of an IT manager, the same operational or economic value propositions.

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