As anyone who’s read any of my previous posts will know, I’ve been considering Red Hat’s adoption of KVM over Xen and wondering if a move to KVM is the right thing to do.
I think “The right thing” depends a fair bit on where you are, and what your requirements are. Obvious? Perhaps, but then sometimes it’s the obvious things we overlook.
I think there’s no pressing need to migrate my hosted server. It works pretty well on Xen and now I’ve sorted out my mess of repo priorities, and I’m a bit less cavalier with updates, I don’t expect it to present me any significant problems.
My home server is a different thing. It’s not currently commissioned so there’s no downtime to worry about, I’d like to be able to run PVM and HVM Windows and Linux guests, including possibly LinuxMCE one day, and carrying most weight for me at present, it’s going to also be my network gateway.
Now, purists might not think running VM services on my gateway is a smart idea, and I should put in a separate host for each, but it’s a model I’d like to try out as I have some work project ideas that might benefit.
My thinking is that if I’m doing security policy, NAT, bandwidth shaping and VPN on a machine that also runs guests, KVM might make sense – doing that work in a Xen dom0 would involve a bit more switching of network data in and out of the Hypervisor and guests. In theory, Linux being the hypervisor should mean it’s only doing that for network traffic to guests, which will only be anything I can’t sensibly run in the base Linux OS.
There may be some argument that my hosted server may benefit too, as in a bonded setup, the current state of Xen networking seems to suggest that the dom0 has to do all the work anyway – I have my dom0 using regular Linux networking (patched to fix an issue bridging a bonded interface) to get my guests on a bridge to a fully bonded interface.
KVM will be an interesting experience to compare with Xen. If the networking is faster, as long as performance of guests is good, it may make sense to choose it ultimately because Red Hat have, and out-of-the-box compatability is no bad thing.
For now, I’m happy to keep my hosted workhorse on Xen and try the new contender out on a home server first.
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