Let's take a step back and look at Xen and KVM. There had been a battle brewing between the two, but with the recent decision to add Xen to the Linux core (KVM is already there), some of that has evaporated. What do you folks make of this recent development?
GILLEN: Over the long term it's more sustainable to have the hypervisor built into the operating system simply because you don't have dual sets of development going on; you don't have to develop a set of drivers for every new piece of hardware that comes out. But commercial support for Xen has waned somewhat. Although Xen is the third most widely used hypervisor, the problem is there's no one single version of Xen used across these different places. Over time, it's going to be more and more difficult to sustain that Xen development effort. I'm not suggesting Xen folds up shop and goes home a year or two years from now. It's a safe bet Xen's going to stay around for the rest of the decade.
KIM: We've got a number of customers that are deploying production workloads in Xen, so we can't abandon them.
GILLEN: Abandonment is probably too strong of a word. I think that over time Xen becomes seen as more of a legacy solution and, although it continues to be used and supported, over time users wind up going to some other environment.
JOLLANS: I think a lot of this is about the community and about the ecosystem. If Xen diverts into multiple code bases then you don't get the same sort of community effects here. With KVM, along with SUSE and Intel and HP and Red Hat and a number of others, we put together a couple of groups recently: the Open Virtualization Alliance, which is looking at how do you educate the market about KVM, and more recently oVirt, which is about getting virtualization management to a common code base as well. So if you can hold the communities together and develop a single code base, then I think long term you've got a much better future than if it diverges into several code bases.
GILLEN: Frankly that's one of the reasons why I have concerns about Xen. Xen is widely used in the service provider community, but they're not using Oracle's or Citrix's version of Xen, they're using open source Xen. They got the bits and they modified them and they've built management tools around it. You can almost call it a fork of the Xen line because they've gone off and done their own thing and those things don't re-converge very easily. As a result, you don't have one large ecosystem, but rather a series of smaller ecosystems.
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