[Lustre-discuss] Lustre on mpath devices

[Andreas Dilger]

On Oct 25, 2007  13:37 -0700, Klaus Steden wrote:
> 
> > That depends...  It depends on what "blkid -t LABEL={fsname}-OST0001"
> > returns.  It _should_ be smart enough to return the DM device, but
> > it is prudent to make sure of this.  There shouldn't be any problem
> > with mounting the Lustre filesystems by LABEL= (which is one reason we
> > moved to a mount-based setup).
> 
> I just checked out my local system and it's returning a regular device name
> (/dev/sdh, or /dev/sdi, depending on the label) and a unique UUID, but then
> I didn't enable multipath when I built the FS.

If those devices (sdh, sdi) are actually part of the multipath device, then
you should NOT use mount-by-label, because the "blkid" tool is using the
same mechanism for locating devices as "mount" will be.

> If I avoid using the /dev name, is it still possible to build failover
> properly if I'm not using the multi-path framework? If it's not, is a
> rebuild of the filesystem required in order to enable multi-path support?

The use of Lustre failover is completely orthogonal to multipath.  The
multipath is a local-node mechanism, and failover is between different
nodes.

As for changing the mount device - this should work, but you might need
to fix up the lustre config on the OST/MDT.  Cliff?

Cheers, Andreas
--
Andreas Dilger
Sr. Software Engineer, Lustre Group
Sun Microsystems of Canada, Inc.