Can anyone explain why most of the VPS hosts are using Xen even though KVM is now coming up fast with Redhat behind it?

Do you have any stats on KVM's emerging popularity? To read about KVM.

I think you see Xen's popularity today due to it's maturity which has more 3rd party vendor support for control panels, but I expect that to equal out over the next year with all the support behind KVM.

No I don't have any stats unfortunately but with Redhat switching their focus from Xen to KVM it must mean something.

Yep that makes sense - now I am wondering if there are any technical benefits (apart from Redhat pushing the tech forward) to switching?

Good question. I recently built an Ubuntu Cloud on my small test cluster just so I could see what all the fuss was about over this "cloud" thing, and maybe it is just the way it is implemented, but KVM was seriously lacking as each instance I deployed would take a CPU core and dedicate it to that instance.

I can see a call for a feature like this, but that sort of defeats the whole shared computing benefits out the window. Building that small test cloud also opened my eyes that "cloud" is not reality, it is marketing hype for VPS. With the one exception, ala carte billing for resources.

Until there is a multi-machine hypervisor, cloud is meaningless. Argue about it all you want, anything you can do in something billed as cloud can be done in VPS clustering.

In our tests, we found that Xen handled many concurrent VMs better than KVM. KVM seemed to suffer a larger performance penalty than Xen as the number of VMs on a host increased.

This is interesting as many point out the better performance of KVM compared with other platforms..

We have seen awesome performance from KVM. We have been using it in production for over a year.

I saw this the other day and thought back to this thread

http://docs.redhat.com/docs/en-US/Re...mitations.html

Hmm, that seems like a serious limitation for those offering VPS accounts.

So far we've only used Xen for clients, OpenVZ to partition some of our own sites.

For what it's worth KVM is supported by solusVM now.

We are looking at offering KVM in the near future. The fact that SolusVM supports it now is a huge bonus. Good to know about the CPU overcommitment.

KVM and Xen PV are too different to compare. A better comparison would be Xen HVM and KVM. We found that KVM had some performance benefits, and the Red Hat backing is also a plus.

Both two entirely different setups.

We have yet to play around with KVM. Xen is very good though but a pain for templates.

I have not really looked into the differences, but that may change once it's mature. I liked Xen setup for SolusVM nice and easy, I thought there were some limits to KVM though.