On 07/28/2012 06:46 AM, Antonis Christofides wrote:
Hi,
short questions:
Is it possible to dictate that resource R1 runs on a different node
than resource R2?
Yes.
http://www.clusterlabs.org/doc/en-US/Pacemaker/1.1/html/Pacemaker_Explained/ch06s04s02.html
Is it possible when moving R1 from node N1 to N2 to first start it in
N2 and only after it starts to stop it in N1? Is it possible to run R1
at the same time in all nodes, and restart it in all nodes whenever R2
is started/moved? How about running R1 in all nodes except the node in
which R2 is running?
Maybe, yes, yes. Have you considered clones, coupled with order and
colocation constraints?
http://www.clusterlabs.org/doc/en-US/Pacemaker/1.1/html/Pacemaker_Explained/s-resource-clone.html
Is it possible to achieve the
above order, and how? I.e. a dependence that service A stops in one node
only after service B starts elsewhere.
If you want to start another service that is using your DRBD device
before the other has stopped, then you require dual-primary mode, since
for a moment, both will be primary. At this point, you might as well
have an active/active cluster where both nodes are primary all the time.
If you just want to decrease your downtime window, maybe you can
postpone the move of the DRBD primary from one node to the other (during
which there is necessarily some downtime) by using advisory ordering.
For mandatory orderings, "If the |first| resource is (re)started while
the |then| resource is running, the |then| resource will be stopped and
restarted.". Not true for advisory orderings.
http://www.clusterlabs.org/doc/en-US/Pacemaker/1.1/html/Pacemaker_Explained/s-resource-ordering.html
http://www.clusterlabs.org/doc/en-US/Pacemaker/1.1/html/Pacemaker_Explained/ch06s03s02.html
The idea would be that you order your DRBD promotion after starting your
resource that changes the routing, with an advisory rule. Not sure if
that works or not, but something to test.
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