I currently use Xen in production to run a number of Ubuntu VMs (Intrepid/Jaunty). I've got another server which I'd like to set up as a VM host to run more guest OSes, and am looking for the best options for our requirements:
- Ability to run 64-bit "modern" guest operating systems (especially Ubuntu Lucid) - we currently have a problem in that we don't have support for Lucid in our existing Xen setup without some serious rebuilding / updating.
- "Bare-metal" / headless configuration - a low-resource host system upon which we can run a dozen or more guests
- Deploy VMs from a "master" image - we can do something like this with Xen now, and it's very convenient for provisioning new stuff
Would also like to have some kind of GUI management tools, if that option exists...
There are probably some other things we'd like to have that I can't think of at the moment, but those are the two most prominent, and most difficult things to accomplish.
I'm open to any other solutions: KVM, OpenVZ, etc... anything that can hopefully meet the requirements above. As far as the host OS goes, we're currently running Debian, but I have no attachment to that. We've been trying to get Xen running on CentOS or Debian Lenny to no avail, we just want something that works. Any suggestions / advice would be much appreciated.
KVM with virtio network and block devices managed via libvirt. Fits all your needs, has performance characteristics similar to Xen, and allows graphical management via e.g. virt-manager (which you can also use to manage Xen hosts, if desired).
As host OS I would suggest Ubuntu Lucid, Debian Squeeze, or Debian Lenny with backported packages (in this order). KVM/libvirt development progresses at a steady pace, so you typically want fresher versions than availably in vanilla Lenny.
Adoption of KVM is strong enough so that you will easily find suggestions and help for most questions you might encounter.
If you're not opposed to a commercial solution, you could look at something like Citrix Xenserver. The free version (Citrix Xenserver Free) is unlimited in terms of VM/host capacity, it supports shared storage and live migration of VMs between pooled hosts;t emplated installs and cloning of VMs; storage snapshots; and it has a graphical management tool.
We've been using KVM on Debian Lenny for a while now. Rock solid and didn't have any of the niggling issues that we had with Xen.
As for hardware, we're currently using the Dell R510s with 12 drives in RAID10 and 64GB RAM. We find we're able to get around 20 on one of these pretty easily using a combination of paravirt and HVM guests.
HTH.
KVM has already been mentioned, but for templates and rapid VM deployment, I suggest you take a look at RHEV - it's not free, but it does get you there.