Xen vs KVM?

NetworkFlag-Sam said:
Can anyone explain why most of the VPS hosts are using Xen even though KVM is now coming up fast with Redhat behind it?
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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.
 
Hostigation said:
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.
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Yep that makes sense - now I am wondering if there are any technical benefits (apart from Redhat pushing the tech forward) to switching?
 
NetworkFlag-Sam said:
Yep that makes sense - now I am wondering if there are any technical benefits (apart from Redhat pushing the tech forward) to switching?
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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..

akliz-larry said:
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.
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akliz-larry said:
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.
Click to expand...

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

http://docs.redhat.com/docs/en-US/R...rtualization_limitations-KVM_limitations.html

CPU overcommit
It is not supported to have more than 10 virtual CPUs per physical processor core. Any number of overcommitted virtual CPUs above the number of physical processor cores may cause problems with certain virtualized guests.
Overcommitting CPUs has some risk and can lead to instability. Refer to Section 31.4, “Overcommitting Resources” for tips and recommendations on overcommitting CPUs.
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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.
 
Vps host prefer using Xen because of the following good things :-
1. XEN performs extremely well with microbenchmarks giving upto 90% of the performance of native, which is excellent.
2. XEN has excellent management tools -xm.
3. XEN user and developer community is very active with almost 150 mails a day.
4. Has a bigger corporate presence.
Whereas Kvm is not very stable yet , runs with QEMU , Performance is not very good and Came late into the scene.
 
Yes, Xen is more widely used simply because of its slightly better performance, advanced stage of development, and support by third parties.
 
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