Like others have already said, you've asked this question on a
Xen list, and you may want to ask on a RHEL or KVM list to get another
viewpoint.
We use Xen today extensively. For what it's worth, here
are my observations and opinions in no particular order:
-
If you use a commercial cloud provider like Amazon EC2 or
Rackspace Cloud, you probably already use Xen (at least the domU) and may not
have a choice.
-
Xen supports paravirtualization without qemu assistance and
without hardware support. This may be an advantage if you are on older
hardware, or wish to tailor a stripped-down distribution to run as a domU (e.g.
you can build a Linux paravirt kernel without most hardware drivers, or a
stubdom based on miniOS). It's fascinating to me how truly small yet
functional a domU can be.
-
The Linux kernel is big. Very big. I don't have a
technical argument not to place the hypervisor inside Linux (as in KVM) but find
it more aesthetically satisfying to separate the hypervisor from the
kernel. The Xen hypervisor is quite small, consisting of a text section under
900KB on my x86-64 hardware. (I also wish Linux were smaller but don't
see that trend reversing soon.)
-
The Xen hypervisor has its own scheduler that runs independent
of the Linux process scheduler, potentially yielding more flexibility in system
configuration and optimization. KVM however relies on the Linux process
scheduler to switch domains, as I understand it. (I'll avoid arguments
whether the Xen or KVM/Linux scheduler is superior for typical workloads.)
-
The argument that KVM is integrated with the kernel and Xen is
not is becoming moot. Thanks to new pv_ops kernels and Jeremy Fitzhardinge's
efforts to merge with the upstream kernel, Xen will soon be as usable with the
latest kernels as KVM.
-
Red Hat's reasons for embracing KVM seem odd, and possibly a
little bit of "NIH" syndrome. With enough work I'm certain KVM
can be as good as Xen, or better, in terms of features and support.
Whatever problem they had with Xen, are we supposed to believe finishing KVM
was less effort than merging Xen?
In the end I don't know that we needed two hypervisors that are
so similar, but we have them. It's going to come down to something like
choosing between Intel or AMD. One might have a slight edge over the
other at any moment, or be somehow more elegant than the other, but both are
very capable and you can do a lot with them.
Jeff
From:
xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Arpan Jindal
Sent: Wednesday, April 21, 2010 1:20 PM
To: Xen List
Subject: [Xen-users] RHEL xen vs kvm
Hello all
needed your views and review on which one is better on RHEL
xen or kvm ?
