[Pacemaker] resource dependency

[Matthew Palmer]

On Fri, Nov 20, 2009 at 02:42:29PM -0200, Alexandre Biancalana wrote:
>  I'm building a 4 node cluster where 2 nodes will export drbd devices
> via ietd iscsi target (storage nodes) and other 2 nodes will run xen
> vm (app nodes) stored in lvm partition accessed via open-iscsi
> initiator, using multipath to failover.
> 
>  Configuring the cluster resources order I came up with a situation
> that I don't find a solution. The xen vm resources depends of iscsi
> initiator resource to run, I have two iscsi initiator resources, one
> for each storage node, how can I make the vm resources dependent on
> any iscsi initiator resources ?

Personally, I think you've got the wrong design.  I'd prefer to loosely
couple the storage and VM clusters, with the storage cluster exporting iSCSI
initiators which the VM cluster then attaches to the VMs as required.  Put
the error handling for the case where the iSCSI initiator isn't available
for a VM into the resource agent for the VM.  To me, this seems like a more
robust solution.  Tying everything up together feels like you're asking for
trouble whenever any failover happens -- everything gets recalculated and the
cluster spends the next several minutes jiggling resources around before
everything settles back down again.

- Matt