I wanted to chime in on the Xen vs. KVM discussions, and give you some food for thought.
I've been using Xen now for years, having replaced UserModeLinux on my personal server, and it's seen a lot of production use at my current job.
That said, KVM is ultimately the right way to go. Constant maintenance of Xen's hypervisor kernel is what causes Linux distributions grief with Xen. Those that keep doing it, do so because it's performant, tested and well-understood.
So you're stuck wondering which virtualization technology you should pick. Here it is: libvirt (with Xen).
Base your toolset, deployment, configuration, and maintenance on libvirt, and use the Xen hypervisor for now.
libvirt provides an easy upgrade path from Xen to KVM once KVM's performance and stability have been battle hardened. Same virtual machine configuration, same provisioning, same disk images. Just grab a new kernel, change which hypervisor you're using and you'll be in the land of tomorrow.
Thursday, April 02, 2009
Xen vs KVM
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4 comments:
On the flip side of this, I'm just entering the linux virtualization arena, and it's the tooling that's mattered most to me. I'm using Ubuntu, which provides extremely high-quality tools for creating libvirt VMs. I don't actually care about KVM vs Xen - I just want my VMs to start up with a minimal amount of administrative work on my part.
This has historically also been where VMWare does well: their virtualisation technology is alright, but the tooling is actively good.
VMware's sysadmin tooling is top notch, but with ESX being a black box, it makes finding people who are skilled at troubleshooting 'weird issues' much harder to find.
Tools like cobbler, func and puppet make managing bulk servers a lot easier, and with the virtualization problem space being better understood, I think these tools will only continue to improve over time.
Upgrade to KVM? The darn thing isn't even stable or scaleable. Nor indeed is there a decent formal definition of libvirt, unlike the DMTF SVPC CIM interfaces, which at least will be known to also work on VMware, XenServer and Hyper-V. Why not map to something that the rest of the industry is using?
Not yet it isn't, which is why if you're flipping a coin over Xen or KVM, there's really no choice.
A CIM interface for libvirt is also in the works: http://libvirt.org/CIM/ ..how far along it is, and what tools it interoperates I can't say.
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