[Lustre-discuss] MDS

[Brian J. Murrell]

On Tue, 2008-08-05 at 01:12 -0400, Mag Gam wrote:
> What is a good MGS/MDT backup strategy if there is one?
> 
> I was thinking of  mounting the MGS/MDT partition on the MDS as ext3
> and rsync it every 10 mins to another server. Would this work? What
> would happen in the 9th minute I lose my MDS, would I still be able to
> have a good copy? Any thoughts or ideas?

Peter Braam answered a similar question and of course, the answer is in
the archives.  It was the second google hit on a search for "lustre mds
backup".  The answer is at:

http://lists.lustre.org/pipermail/lustre-discuss/2006-June/001655.html

Backup of the MDT is also covered in the manual in section 15 at

http://manual.lustre.org/manual/LustreManual16_HTML/BackupAndRestore.html#50544703_pgfId-5529

Now, as for mounting the MDT as ext3 (you should actually use ldiskfs,
not ext3) every 10 minutes, that means you are going to make your
filesystem unavailable every 10 minutes as you CANNOT mount the MDT
partition on more than one machine and we have not tested multiple
mounting on a single machine with any degree of confidence.

Of course Peter's LVM snapshotting technique will allow you to mount
snapshots which you can backup as you describe.

But if you are going to have a whole separate machine with enough
storage to mirror your MDT why not use something more active like DRBD
and have a fully functional active/passive MDT failover strategy?  While
nobody in the Lustre Group has done any extensive testing of Lustre on
DRBD, there have been a number of reports of success with it here on
this list.

b.

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