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Xen vs KVM : A Healthy Discussion
MetroVPS_NMP
Host Rep, Veteran
in General
Hello,
Everyone is using KVM now for the features it offer. But, I have some real life experience between Xen & KVM.
In KVM, I have got two major drawbacks. These are, the Disk Speed remarkably gets lower on the VM comparing to Host Node itself. Another is, if any VM gets higher server load, it affects all other VMs.
In comparison, I haven't seen such drawbacks in Xen.
What's your experience ??
Comments
Are you doing side-by-side comparisons of your own hardware with set control variables?
If you are simply comparing experiences at different cloud providers, I think your issues are not because of the architectures themselves but rather overselling.
kvm is replacing xen and openvz.
I have got both experiences. From other providers & from own setup. Specially, the load & impact experience. This is why I have come here to find out the issue.
The fact that Amazon use Xen on their infra is a bug thing. But bigger thing is that they move to KVM. And their researchers are way better than us. So KVM > Xen. Thought, I feel nostalgia towards Xen
It 100% depends on your use case and also you need to do a little research on current state of Xen. Effectively if you run a 'HVM' or full virtualization server on Xen, for a while now they have just been leveraging a version of QEMU, so its actually using KVM for full virtualization. Why I say it depends on your use case is, where you really see the performance gain when using Xen is when you use PV mode and run Linux hosts, PV for Linux based servers can be a lot more performant than KVM in some cases because of how CPU, memory and IO resources are shared under paravirtualization vs QEMU.
For me (personally), I run all Xen nodes cause it makes for setting up easy KVM servers as well as allows me to leverage the optimizations from paravirtualization for Linux servers, allowing slightly better performance overall.
KVM adds overhead, so when you leverage paravirtualization you don't have that extra overhead and have more direct access to memory, cpu and IO resources which allows slightly better performance overall.
my 2 cents.
Cheers!
Ah, You explained like a charm. Thanks, Mate.