Arch Linux

lukea

Member

Registered: 2008-12-12

Posts: 2

Linux Kernel Virtual Machine (KVM) vs Xen

I am currently researching the options open to me for Virtualisation, the two main ones I have seen are Xen or KVM.

I mainly use CentOS (RHEL), but have read that the version of Xen with it is very old, broken and unstable. KVM isn't included in the kernel that ships with CentOS, as it is too old, apparently it was first featured in Kernel v2.6.20. There isn't likely to be an update till RHEL6, which is due for release first quarter of 2010. I can't wait over a year, so need to find another Distro for use as the Host OS/Hypervisor.

I have built a pretty powerful server, it has an Intel Xeon 3230 which has VT - so I might be better off using KVM over Xen. I am going to collocate this server, so realistically I can make this decision only once - as it would be a PITA to re-install a host Linux distro remotely.

I did a search on distrowatch for distros with the latest version of the kernel, and Slackware came up as being just one minor version behind the most current (v2.6.27.7). Now this distro is very mature, so should be a fairly safe bet, but it is a 32bit version and can't host 64bit VMs. I have 8GB of ram so want to be able to use it all, and offer the choice of 32/64bit VMs. So that's that out of the window.

I have used Arch Linux on and off for a couple of years as a workstation OS, but because it is so bleeding edge, when pacman updates it can break itself. But I suppose if I just use it as the Host OS, and never let it update/reboot, then it won't break. It should be fairly lightweight and stable, as I will be installing the bare minimum packages. I have a management card, so if the server fails to boot, then I can still remote in to fix it. If I do want to update the kernel, is it possible to update without rebooting? I think it is somehow... unless I can just reboot during an unused time at 3am or something.

As you can tell I am leaning towards KVM on Arch Linux (x86_64). Is this a good plan?

iBertus

Member

From: Greenville, NC

Registered: 2004-11-04

Posts: 2,228

Re: Linux Kernel Virtual Machine (KVM) vs Xen

Many criticisms of Xen can be found with a simple Google search. The biggest one seems to be the need to modify guest OS code to make it run properly with Xen, but that is going away as Xen adds support for AMD-V and Intel VT technologies. KVM is coming on strong in the virtualization market now and seems to be the accepted choice.

That said, I'm not sure how you would setup the machine to properly host VMs with KVM.

Also, you may want to Google kexec to research that restarting the kernel without rebooting idea.

rine

Member

From: Germany

Registered: 2008-03-04

Posts: 217

Re: Linux Kernel Virtual Machine (KVM) vs Xen

I also recommend kvm. I've been trying to get a debian guest with kernel 2.24 running in xen (and I didn't succeed). kvm is just way less intrusive and you can pretty much use whatever you want as guest OS. For the host I'd take debian etch, but that's probably just because we use it at work for almost all servers (centOS for trixbox) and I don't really have experience with other systems. The newest kernel in the repos is 2.24. If you don't need anything newer, I don't see a reason not to use etch, as it's very stable.

lukea

Member

Registered: 2008-12-12

Posts: 2

Re: Linux Kernel Virtual Machine (KVM) vs Xen

I looked on DistroWatch to find one that had a Kernel version of at least 2.6.20, and it still says it is 2.6.18 - which is why I originally discounted it. I then searched the Debian website, and it does appear 2.6.24 is the latest kernel version for etch (stable), which is good enough to let me use KVM.

I will use Debian for the host. Thanks for the headsup rine!