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.
Kim: I think with the recent acceptance of Xen into the Linux kernel we're beginning to see more community support for Xen, so maybe less diverging and more converging.
Jollans: The other thing to remember is there is an architectural difference between Xen and KVM and I think they each have their strengths. Xen's approach is they write to their own very small footprint hypervisor, so they're writing all the core services as tightly as possible to provide that platform. The KVM approach is to leverage Linux and then strip it down from there. And depending on what you want to do, one may have a strength or the other may have a strength.
NWW: Al, who has what market share?
Gillen: VMware is number one, Xen is second, Microsoft's Hyper-V is third.
NWW: How much of a lead does VMware have?
Gillen: Depending on how you measure it, VMware has a little more than half of the market.
NWW: How hard will it be for the rest of the camps to make headway against VMware?
Gillen: I don't know if that's the right way to think about it. We don't see companies going in and ripping out VMware and replacing it with KVM or something else. We see customers over time start to implement secondary hypervisors. In fact, getting VMware out once it's in is very challenging.
Jollans: One of the fun things about this industry is how fast the technologies move because the rapid refresh rate represents opportunities for new technology to come in. As people bring in new servers, for example, there comes the question, should we continue with the existing hypervisor structure or do we now think this is a time to change to a new hypervisor strategy? So the market shares can change and the whole dynamics of the industry move simply because the refresh rate is happening.
Gillen: I fully agree with Adam. I think if we dial out eight or 10 years from now you're not going to see VMware has contracted to 30% of the market and everybody else is 70%. It's going to be more a matter of the hypervisor market as we think of it today will still exist, but the cloud market will have grown enough that it will become the metric we're measuring.