Hot backups

[Simon Matter]

> I'm also running into an issue where occasionally the snapshot fails -
> it's taken while reiserfs is in the middle of a transaction, and the
> journal can't be replayed on mount because the snapshot is read-only.
> This is more of an LVM issue than anything else. I get around it by
> syncing the disk before taking the snapshot, and by deleting the
> snapshot and trying again if it's not useable.

I've been using XFS on LVM and I think it doesn't have the problem you
describe. With XFS, you have to call 'xfs_freeze -f' before taking the
snapshot, then you 'xfs_freeze -u' it again.

> I'd love to know of a way to ask cyrus to defer message delivery briefly
> and make sure everything is in sync. That way I could signal cyrus to
> "sync up and pause", do the db conversions, snapshot the volume, and
> resume cyrus. I'd prefer to avoid killing and restarting the master
> during the normal backup process.

Would be nice to have something like a 'cyrus_freeze' command. Maybe there
is a way to do this with SIGSTOP/SIGCONT?

Simon