[Linux-cluster] [clvm] Volume group for uuid not found

[Kaloyan Kovachev]

> > 
> > Yes, it does work in active-active but DRBD people themselves don't
> > recommend running it in production active-active under cluster file
> > system, I quote from their website:
> > "DRBD's primary-primary mode with a shared disk file system (GFS,
> > OCFS2). These systems are very sensitive to failures of the
> > replication network. Currently we cannot generally recommend this
> > for production use."
> > http://www.drbd.org/home/mirroring/
> 

'These systems are very sensitive to failures of the replication network' is
the key problem here, but if you use the same interface for cluster
communication the node would be fenced in such cases and then DRBD will
gracefully recover

> That surprises me - it could just be an out of date page. I've used it 
> in active-active mode with GFS on top in all sorts of harsh and abusive 
> edge-case ways and never saw it skip a beat.
> 

if cman is not running on the node sometimes i get in the logs:
block drbd0: istiod1[3173] Concurrent local write detected! [DISCARD L] new:
0s +1024; pending: 0s +1024
but this can be ignored and when cman is running all is fine in active-active
mode even with multipath in multibus mode for both storages

so in short DRBD is OK with shared GFS in active-active, but you should keep
cman (fenced) running on the node, use the same (dedicated) network for DRBD
and cluster communication and as an additional precaution you should wait for
all DRBD resources to became Primary on both nodes before you start using the
file system to avoid corruption.