[Pacemaker] Fencing libvirt/KVM nodes running on different hosts?

Andrew Beekhof andrew at beekhof.net
Mon Nov 28 17:38:01 EST 2011

On Tue, Nov 29, 2011 at 6:55 AM, Andreas Ntaflos
<daff at pseudoterminal.org> wrote:
> Hi,
> Scenario: two physical virtualisation hosts run various KVM-based
> virtual machines, managed by Libvirt. Two VMs, one on each host, form a
> Pacemaker cluster, say for a simple database server, using DRBD and a
> virtual/cluster IP address. Using Ubuntu 10.04 and Pacemaker 1.1.6, with
> Corosync 1.4.2 on the hosts and guests.
> How do I implement node-level fencing in this scenario?
> Can the rather new "external/libvirt" STONITH plugin be used here? It
> seems to me it only supports a single hypervisor URI to connect to and
> expects all VMs/nodes that can be fenced to be running on the same
> hypervisor.
> Looking at http://www.clusterlabs.org/wiki/Guest_Fencing it says that
> fencing guests running on multiple hosts is not supported in
> fence-virt/fence-virtd.
> What are my options here? How do other people manage node-level
> fencing/STONITH when the nodes are VMs and running on different physical
> hosts (which seems like the sensible thing to do, considering a single
> host is a SPOF)?
> Sorta related question: are Pacemaker clusters based on virtual machines
> (and Libvirt) really so uncommon that there isn't a quasi-definitive
> answer to this? Like "If you use Libvirt, implement fencing by using
> this or that STONITH plugin."

You could try fence_xvm or fence_virt from the RHCS set of stonith
agents (which pacemaker also supports).
I believe it also handles the case when the guest could be on one of
multiple hosts, personally I only use it for a single host.

Lon might have some documentation pointers...

> Thanks in advance,
> Andreas
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