best practices for kvm setup?

best practices for kvm setup?

[Rik Theys]

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? 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?

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?

Regards,

Rik


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Re: best practices for kvm setup?

[Dor Laor]

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
>
>
> Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm
>
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