Hyper-V R2's 'boatload' of new features

Microsoft's Hyper-V R2 virtualization has a 'boatload' of new features. A virtualization expert discusses two standouts: Cluster Shared Volumes and Live Migration.

Welcome to the SearchServerVirtualization.com podcast about the new features in Microsoft's Hyper-V R2 and System Center Virtual Machine Manager R2. I'm site editor Colin Steele, and our guest today is Greg Shields, a partner with Concentrated Technology and a Microsoft MVP.

Colin Steele: Thanks for joining us, Greg.

Greg Shields: Thank you, Colin.

Steele: Greg, Microsoft will release Hyper-V R2 in October and the feature that most people are looking forward to is Live Migration. Can you tell us how Live Migration is different from the Quick Migration feature that was offered in the first version Hyper-V and how it will benefit users?

Shields: Well, I'll tell you that Live Migration is … you're right in saying that it's one of those features that a lot of people are looking forward to. When Microsoft released Hyper-V version one back with the original release of Windows Server 2008, that essence of Hyper-V had the ability to fail over from one host to another. They're similar to VMware's VMotion technology.

Now, what was different in that original version, and the new version is that in order to do one of those failovers, there was a little bit of time delay where the server would actually sort of pause, going into a port server pause state, and that pause state could occur anywhere from eight seconds to 32 seconds or maybe even a little bit more. And it was based on the amount of associated RAM, the attached RAM you have on a virtual machine.

Now, that was OK for a lot of people, but for some people, knowing you're going to have a slight downtime when you did that equivalent of a VMotion, that really did not work in many people's minds. So, with the R2 release of Windows Server 2008, Microsoft actually created a migration, this Live Migration, which now, more or less, functions similar to what the effects people see with VMotion. The difference is when you think about when people are doing a Live Migration or a VMotion or any of those technologies that allow people to fail over virtual machines from one host to another.

The first version that Microsoft brought out -- it took a long time because there's an amount of copying that's involved -- a copying over of a server's RAM from one host to another. That period of time, like I said, relates to how much RAM is on the computer, and it's because it takes that amount of time to actually copy that amount of RAM.

Well, the difference with version two is that there's now a pre-copy function that's built into the OS that allows the server to continue operating while most of the RAM gets copied from host to host. The effective result is that when the actual … the owner of that virtual machine shifts from one host to the other, you're going to lose, you know, a packet or so whenever that completes. So, again the real difference is, more or less, we are reducing the amount of time it takes to complete a migration from one host to another.

Steele:What are Cluster Shared Volumes [CSV], and what role do they play in Live Migration?

Shields: You know another one of the features that really didn't happen with the original release of Hyper-V was this concept of a cluster-aware file system. If you think about it … think of the NTFS [NT file system] for a minute, the NTFS file system has been around for a long time. It's a useful file system that works on, more or less, every Windows system in existence.

The problem with the NTFS file system is that there's no capability for two different hosts to look at the same volume and be able to understand who owns which files. There are other third-party systems out there that allow this to happen, but this isn't one of the tools that is available in NTFS. Now, Microsoft has, more or less, standardized on NTFS as the file system which is used by its cluster service, and because that cluster awareness wasn't there, they had to develop, kind of like, a rapid layered over the top file system that allowed multiple hosts to know who owned which files.

Now the Cluster Shared Volumes is available for any cluster, you can turn them on in any cluster in R2, but they're really designed for use by Hyper-V, because Hyper-V has a very small number of files that you would have in a certain volume. The end result is that with the first version of Hyper-V, you could only install one virtual machine per connected LUN [logical unit number], which is actually kind of like a pain in the neck for some people. With version two of R2, you can create one big LUN with lots of virtual machines on it, and they can fail over individually.

Shields: Are there any scenarios where third-party cluster file systems would be more appropriate?

Shields: There are always scenarios where you may be able to jump out of the traditional Microsoft solution. Microsoft is well-known for providing a good-enough solution, if you need something that's got, you know, extra capability you can jump to a third-party solution. That's been their business model for a long time. Now, again, as I mentioned before, the CSV feature in R2 is not really a new file system per se. It's, as I said before, it's a layering on top of that file system with a little bit awareness of which files are owned by which host.

Now, if you want a true cluster-aware file system, you're going to need to go to a different vendor out there, you're going to need to go to a Sanbolic, for example, or one of the other cluster-aware solutions that are supported by Microsoft. Those are going to have a little bit more storage management capabilities; they're going to have a little bit more capabilities for replication if you have a stretch cluster between multiple sites. And it will be a little bit easier to use especially if the size of your cluster gets much, much larger.

Steele: You talked about this a little earlier, but why did the first version of Hyper-V only had a limit of one VM per LUN, and how will that change in R2?

Shields: Again, it has everything to do with that cluster file system. You know, if you think about it … think about a Windows cluster, alright, when you look at a Windows cluster, a Windows cluster can fail over a resource when a function or a component of that resource fails. One of the components of a virtual machine resource is its disc. Now, if I … in the old original version if I failed over a disc that had multiple virtual machines on it, well it would take all the virtual machines with it. So, I would essential have to fail over every VM on that LUN to be able to get it from on to the other. Well, you don't really want to do that especially if you have lots of virtual machines on one line. You want the very discrete capability of failing over one VM and maybe not another. Now, in R2, now that we have this cluster shared file system, that allows us to not necessarily failover the entire LUN but the individual files on that LUN.

Steele: And, finally, Greg what are some of the most important new features in System Center Virtual Machine Manager R2?

Shields: Oh, there's a whole boatload of new features in R2. Honestly, the most important new features are those that are align with Hyper-V and the management of Hyper-V. I don't want to go into specific details; you can pick up the specific details on Microsoft's website. But be aware that the important thing about VMM [Virtual Machine Manager] is your ability to work with, to manage multiple Hyper-V hosts sort of as a group, right. I can have five or six or eight different Hyper- V hosts and work with them as a group and not have to go to individual Hyper-V consoles to work with them.

Now, because we have this much better migration capability and because we have this cluster-aware file system, when we layer VMM over the top, we now have a much better way of looking at our virtual machines, identifying their performance, balancing them so they have the right load balanced across all of them and, really, doing a better job of managing those virtual machines as a group. That's really what you get out of VMM. When you align VMM R2 with the new features in Hyper-V version two, that's when you get the biggest bang for the buck in being able to operate these machines as a cohesive group.

Steele: Microsoft's MVP, Greg Shields, thanks for your time. To our listeners, if you'd like to find out more about concentrated technology, you can visit them at www.concentratedtech.com

I'm Colin Steele. Thanks for listening to the SearchServerVirtualization.com podcast.

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