[virt-tools-list] question about clustering

[Kenneth Armstrong]

Ok, thanks.  I'll dig into this further and do some test runs.  Is
there a libvirt/kvm/clustering specific mailing list I could take this
to should I run into issues?

On Mon, Feb 21, 2011 at 4:22 AM, Josip Deanovic
<djosip+news at linuxpages.net> wrote:
> On Sunday 2011-02-20, Kenneth Armstrong wrote:
>> Ok, so rebooting from within the guest OS itself might not be bad,
>> since the PID remains the same?  So RHCS is basically checking for the
>> PID on a vm's instance then?
>
> AFAIK, RHCS is checking the state of a VM using virsh.
>
> So if you poweroff/power on your vm there is a chance for rgmanager to get
> the status while your VM is "shut off", although it's a very short time.
>
> About the PID of a VM...
> Generally rgmanager is using a good logic. In case you add your VM to
> cluster configuration, start VM manually using virsh and then you try to
> start it through clusvcadm, rgamnager will check all the nodes and if it
> find out VM is already running, rgmanager will not start another instance of
> your VM. It will just print out warning and inform you that your VM is now
> started on some specific node.
>
> Because RHCS is using virsh to check the state of VMs, there is also a
> danger of restarting libvirtd through nodes in a cluster.
> Documentation of rgmanager states that if you want to restart (or stop)
> libvirtd daemon, you must freeze VMs on that node.
> Freezing of VMs doesn't mean VMs will be blocked, it means cluster will stop
> checking the state of these VMs (domains) until your unfreeze them.
>
> Check these links for details about rgmanager:
> http://sourceware.org/cluster/wiki/VirtualMachineBehaviors
> http://sourceware.org/cluster/wiki/RGManager
>
>
> P.S.
> This is now a bit out of the scope of thid mailinglist.
>
>
> --
> Josip Deanovic
>