Greetings,
* Paul Förster (paul.foerster@gmail.com) wrote:
> > On 26. Jun, 2020, at 12:29, Magnus Hagander <magnus@hagander.net> wrote:
> > I believe NetApp does atomic snapshots across multiple volumes, if you have them in the same consistency group. (If
youdon't then you're definitely in for a world of pain if you ever have to restore)
> >
> > Snapshotting multiple volumes in a consistency group will set up a write fence across them, then snapshot, and AIUI
guaranteescorrect write ordering.
>
> That's how I understood it too. But it will be difficult in our complex storage world to get the storage guys to
createa consistency group.
>
> Also, what I'm looking for is a plugin that allows to, how Netapp call it, "quiece" the PostgreSQL cluster, i.e. does
start/stopbackup.
Presumably they mean 'quiesce', except that that *isn't* what PG's
start/stop backup calls do, and assuming that's what happens is quite
wrong and could lead to issues.
The PG start/stop backup calls do things like wait for a checkpoint to
happen and track when that checkpoint was and return that info along
with whatever the stopping point of the backup is- so that you can make
sure that you have all of the WAL between those two points, and so you
can create the backup_label file that's needed to indicate on restore
that you're restoring from a backup and not just doing crash recovery.
If it isn't an atomic snapshot across everything then start/stop calls
have to be done as well as all that other fun stuff.
> I don't really trust the community plugin as it is so old and I'm not sure it gets any more development attention.
Forexample, what about the API change (exclusive vs. non-exclusive)? Does it use the new API?
No clue.
Thanks,
Stephen
