[Linux-cluster] Startup and Shutdown of a Virtual/Physical cluster

[jr]

Hi Paolo,


> When the physical cluster starts up, and the nodes are operational, the
> virtual nodes are started in an unordered mode, e.g. the allocation to the
> physical nodes is not predetermined. If the physical cluster nodes come up
> at different times, the first operational node of the physical cluster
> tries to bring up all the virtual guests, even if the available memory is
> not sufficient. This causes some instabilities at system startup, and
> requires some manual intervention in order to distribute the xen guests
> among the physical cluster nodes.
> 
> Is there some way to prevent this kind of behaviour ?
> 

yes there is. Basically what you want to do is the same thing that is
done with nfs services in the nfs cookbook.
you basically create three failoverdomains, one for each node, with
ordered=1, then put your nodes in with a priority of 2 except one node
which gets priority of 1. every domain then has to have a different node
with the priority of 1. 
then all you have to do is put the vms in the failoverdomain with the
node you want it to be started on automagically, so in case you have
failoverdomain1 with node2 having priority 1, you put
domain="failoverdomain1" in your <vm> definition.
this will also do some migration magic if your cluster is up. so if a
node has to take over a vm that's in a failoverdomain with a failed node
having the highest priority, it will automatically migrate the vm back,
once the higher priority node has become available again.


> Another aspect is related to system shutdown. My system is powered by an
> UPS, but once in a year due to maintenance on the power supply it may
> happen that there is need to shutdown the system, or in case of blackout
> with a long time. How is it possible to completely shutdown the cluster by
> UPS command ?

i believe shutting down rgmanager on every node will do the trick. or
else, shutting down cman should work too :)

enjoy,
johannes