[gpfsug-discuss] feature request : ability to run multiple snapshot related commands simultaneously

Sabuj Pattanayek sabujp at gmail.com
Tue May 27 22:29:02 BST 2014


Sometimes snapshot deletions can take a very long time. While they're
running no other snapshot related commands can be run, e.g. it doesn't look
like I can run an mmcrsnapshot on the same fileset while a global snapshot
deletion or a snapshot deletion on the same fileset is ongoing.

Today's snapshot deletion on a global snapshot created about 19 hours ago
is going painfully slowly for some reason. It's also affecting CNFS and SMB
performance with periods of hangs for about 30+ seconds. This is not the
norm on our fs. GPFS access continues to be ok during these NFS/SMB hangs.
Another problem it causes is that snapshots on the root fileset cannot be
created while this global snapshot is being deleted. This disrupts our
daily snapshot creation schedule and I also have to switch to running
mmbackup without a snapshot, since I won't be able to create a new global
snapshot if another global snapshot is being deleted.

If possible I'd request that running multiple snapshot related commands
simultaneously be allowed, at least the ability to run an mmcrsnapshot
while an mmdelsnapshot is running would be nice. I can see that running
multiple global snapshot deletions or multiple simultaneous snapshot
deletions on the same fileset would be risky/very difficult (or impossible)
to implement but it seems like it should be possible to "quiesce" an
mmdelsnapshot for a few seconds so that an mmcrsnapshot on the same fileset
can be completed. This can be done manually by interrupting an ongoing
snapshot deletion, creating the new snapshot, and continuing the deletion
but would be nice if this could be fully automated . What would be even
cooler would be a snapshot command queuing system for deletion requests
within the same fileset, that way snapshot deletions would be queued up and
automatically occur as soon as deletions in the same fileset are complete.
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