On 9 Nov 2014, at 9:28 pm, Matthias Teege matthias-gm...@mteege.de wrote:
Hallo,
On a cluster I have to place three resources on the same node.
ms ms_disk_R p_disk_R
ms ms_disk_S p_disk_S
primitive vm_srv ocf:heartbeat:VirtualDomain
The colocation constraints looks like this:
colocation vm_with_disk_R inf: vm_srv ms_disk_R:Master
colocation vm_with_disk_S inf: vm_srv ms_disk_S:Master
Do I have to add another colocation constraint to define a
colocation between disk_R and disk_S. I'm not sure because the
documentation says:
with-rsc: The colocation target. The cluster will decide where to
put this resource first and then decide where to put the resource in
the rsc field.
In my case the colocation targets are ms_disk_R and ms_disk_S.
If pacemaker decides to put disk_R on node A and disk_S on node B
vm_srv would not start.
Correct, this is why you need the third constraint - as smart as pacemaker is,
its nowhere as good as a human brain.
So while it is obvious to us that ms_disk_R and ms_disk_S need to go on the
same node, pacemaker will need the extra hint.
Suggestion, do this:
colocation disk_S_with_disk_R inf: ms_disk_S:Master ms_disk_R:Master
colocation vm_with_disk_S inf: vm_srv ms_disk_S:Master
For ordering you want as much parallelism as possible, for colocation - chains
work best.
I use order constraints to start disks before the vm resource.
order disk_R_before_vm inf: ms_disk_R:promote vm_srv:start
order disk_S_before_vm inf: ms_disk_S:promote vm_srv:start
Thanks
Matthias
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