[manvsmachine]

Xen is still widely used. IIRC Xen provides the virtualization layer for AWS, and it is used by some pretty large hosting providers (Linode comes to mind). It also is packaged into a number of commercial commercial offerings. Oracle's VM solution is really just Xen running on Red Hat with some optimizations for their platform stack, same with Citrix. Clearly those two implementations alone is going to be a decently-sized install base.

I don't know how much KVM is used in the wild, but it has been crowned the "official" hypervisor for RHEL and Ubuntu, so I would guess that it it's been steadily gaining steam w/ the OSS crowd.

[pwaring]

KVM is used by Bytemark (www.bytemark.co.uk), who provide virtual machines for hosting (smaller scale than Linode, mostly UK).

[evangineer]

It's worth noting that Bytemark started out as and was for a very long time a Xen shop.

[dgl]

They started out with User Mode Linux actually, before Xen even existed.

[dasmoth]

Indeed -- and stuck with it for quite some time. They were trialling Xen for some time, but I don't think they ever deployed it on a terribly large scale. Certainly, my VM went straight from UML to KVM.

[pwaring]

I believe the management tools for Xen (or lack thereof) were the reason for using KVM instead. None of my machines (I have 7 or 8) have ever used Xen.

[evangineer]

Thanks for the catch, I had forgotten that they were a UML shop.

[pwaring]

They were never a Xen shop, they trialled Xen with a few customers but never rolled it out. This blog post has more detailed info:

http://blog.bytemark.co.uk/2011/02/28/why-we-skipped-xen

[evangineer]

Funny, I did read that article a few months ago but had completely forgotten about it. It's a good read if you're into the virtualisation thing.

[piranha]

New Ubuntu switched to KVM. They don't even supply kernels for Xen now.