[lustre-discuss] ZFS zpool/filesystem operations while mounted with '-t lustre'

[Peter Grandi]

> You only need to stop lustre if you are planning to decommission the old hardware and switch over entirely to the new hardware.  In that case, stopping lustre is needed to ensure that no new content is created on the mdt during the final sync.

Thanks, that was my guess, as that that presentation described a full 
migration rather than an incremental backup situation.

> If you are just trying to keep an on-going backup of the mdt on another zpool, you can just keep doing incremental snapshots and don't have to stop lustre (with the knowledge that your backup of the mdt data will be slightly old).

Good guess, that's pretty much what I want to do. BTW with a 
belt-and-braces approach I also mean to 'tar' and 'getfattr' 
(just-in-case) the same to a different media.

BTW I wonder whether I should bother to do the same for the MGT -- on 
one hand it is tiny, on the other my guess is that its state is pretty 
much irrelevant in case of restoring the MDT.