[DRBD-user] Setup question using DRBD, cluster FS & KVM

Florian Haas florian at hastexo.com
Fri Nov 25 16:53:27 CET 2011

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On 11/25/11 06:23, Trey Dockendorf wrote:
> After reading the documents linked previously, most of the DRBD user
> guide and documents related to Pacemaker, I still have a few conceptual
> questions.
> First, I've seen lots of mention of the requirement to to sync the XML
> data for each VM.  Is this necessary will KVM or Pacemaker be handling
> this?  Right now I typically store all VM disks at /vmstore which has
> the same security context as /var/lib/libvirt/images.  Do I also need to
> replicate the directory containing the domain XML files?

Yes. You can do that by putting those into a separate directory in
/vmstore as well (or on NFS, for that matter), and then use
ocf:heartbeat:symlink to manage your symlinks from /etc/libvirt/qemu. Or
your can just use csync2 to keep the configurations in sync.

> The other questions is do Pacemaker and other services for clustering
> live on the replicated servers or on external systems? As a follow-up ,
> if they live on the replicated servers, do I have to take measures to
> ensure those services stay in sync?

I'm not sure what you mean here exactly, but if your question boils down
to "do I run Pacemaker on my DRBD nodes?", then yes, definitely so.

> Right now I have a good idea of how to structure all this, but just a
> few low level concepts I have yet to fully understand.  So far I think I
> can achieve the necessary failover and live migration for the VMs using
> 2 servers with /vmstore replicated with DRBD.  /vmstore will live on top
> of GFS2 to allow active/active operation.

What do you use for fencing?


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