[lustre-discuss] Lustre snapshots

[Andreas Dilger]

On May 30, 2019, at 01:50, Hans Henrik Happe <happe at nbi.dk> wrote:
> 
> Hi,
> 
> I've tested snapshots and they work as expected.
> 
> However, I'm wondering how the clients should mount without knowing the
> mount names of snapshots. As I see it there are two possibilities:
> 
> 1. Clients get ssh (limited) access to MGS (Don't want that).
> 2. The names are communicated through another channel. Perhaps, written
> to a file on the head Lustre filesystem or just directly to all clients
> that need snapshot mounting through ssh.
> 
> If there isn't a better way, I think number two is the way to go.

You could use automount to mount the snapshots on the clients, when they are needed.  The automount map could be created automatically from the snapshot list.

Probably it makes the most sense to limit snapshot access to a subset of nodes, such as user login nodes, so that users do not try to compute from the snapshot filesystems directly.

> Guess the limited length of Lustre fs names is preventing the use of the
> snapshots names directly?

If you rotate the snapshots like Apple Time Machine, you could use generic snapshot names like "last_month", "last_week", "yesterday", "6h_ago" and such and not have to update the automount map.  The filesystem names could be mostly irrelevant if the snapshot mountpoints are chosen properly, like "$MOUNT/.snapshot/last_month/" or similar.

Cheers, Andreas
--
Andreas Dilger
Principal Lustre Architect
Whamcloud