[Pacemaker] resource dependency

[Matthew Palmer]

On Fri, Nov 20, 2009 at 03:14:16PM -0200, Alexandre Biancalana wrote:
> On Fri, Nov 20, 2009 at 2:53 PM, Matthew Palmer <mpalmer at hezmatt.org> wrote:
> > 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.
> 
> Hi Matt, thank you for the reply.
> 
> Ok. But if I go with your suggestion I end with the same question.

No, you don't.  Whatever you're doing, it's not what I'm suggesting.

> Having the 2 node storage cluster exporting the block device via
> iSCSI, how can I make the VM resource at the VM cluster depend on
> *any* iSCSI target exported ? The standard order configuration just
> allow dependency on *one* resource.

You.  Don't.  Specify.  A.  Resource.  Dependency.  You make your VM RA
handle iSCSI failure internally.

- Matt