[Ocfs2-users] Multiple clusters per node?

[Sunil Mushran]

Søren Kröger wrote:
> I'm trying to split up our big OCFS2 filesystem into 3 separate LUN's, 
> since there are only a limited amount of nodes which need access to 
> the different parts of the OCFS2 filesystem.
> One "Master" server with RW access should still be able to mount all 3 
> OCFS2 LUN's, all others would only mount one of the 3 LUN's in RO mode.

In a distributed lock manager, no one node is the master node for
all resources. Mastery of resources is distributed amongst all the
nodes irrespective of the fact that a node may have mounted ro.

Note that the locks on a resource are only created if a node actually
reads that inode. So it could be that you have three nodes reading
different directory trees that have little in common with each other.
In that case, each node will master the resources and the only lock
on each resource will be the local one.

> What i want is:
> - Lowering the impact, when one node crashes and causes deadlocks on 
> the filesystem for other nodes

When a node crashes, the surviving nodes will recover it. Why should
there be any deadlocks?

> - Lowering the impact, when we have to resize a OCFS2 volume

ocfs2 has online file system resize. However we require a cluster
volume manager. This should be working in SLES11 when they release
the HA extension package. We hope to have this running with (RH)EL6.

> - Lowering the mastery time

Again, ro nodes have as much a say in mastery as rw.

> Is there one master per filesystem or one master per cluster?
> Would 3 separate filesystems under the same cluster be "separated" 
> enough to achieve?