Re: best practices for kvm setup?

[Dor Laor <dor.laor@qumranet.com>]

Rik Theys wrote:
> Hi,
>
> I'm looking into virtualizing some of our servers onto two (or more) 
> physical nodes with either KVM or Xen. What are the 'best practices' 
> for running virtual _servers_ with KVM? Any good/bad experiences with 
> running KVM for virtual servers that have to run for months on end?
>
> I've installed ubuntu 8.04 because it should have KVM as the default 
> virtualization tool and is the only 'enterprise' distribution with kvm 
> right now. I used one host to act as an iSCSI target and installed 
> ubuntu with KVM on two other nodes. I can create a virtual server with 
> virt-manager, but it seems live migration is not (yet) supported by 
> libvirt/virsh? So how are other people running their KVM virtual 
> servers? Do you create a script for each virtual server and invoke kvm 
> directly? How do you do the live migration then? Launch the script 
> with an 'incoming' parameter on the target host, and run the migrate 
> command manually? 
If libvirt does not support migration than you'll need to automate it 
yourself, we use a daemon to exec/migrate VMs. AFAIK, except for 
libvirt* there is no other free tool for it.
> Or is there an other (automated) way? I once tried the live migration 
> on a test host and if I recall correctly, the kvm process kept on 
> running on the source host even after the server was migrated to the 
> target? Is that the expected behaviour?
>
This is works-as-designed, the idea is that a 3rd party mgmt tool get 
the result of the migration process and closes one of the 
source/destination. Without 3rd party, the destination cannot continue 
the source got end-of-migration message and the opposite on failure.

> What type of shared storage is best used with KVM (or Xen for that 
> matter)? Our physical servers will be connected to a SAN. Should I 
> create volumes on my san and export them to my physical servers where 
> I can then use them as /dev/by-id/xxx disk in my KVM configs? Of 
> should I configure my two servers into a GFS cluster and use files as 
> backend for my KVM virtual machines? What are you using as shared 
> storage?
>
We use NFS and it works pretty well, your proposals are also valid 
options. Just make sure an image is not accessed in parallel by 2 hosts.
> Regards,
>
> Rik
>
>
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