Greetings,
* Paul Förster (paul.foerster@gmail.com) wrote:
> When I wrote our backup mode script I read the deprecation note about the exclusive mode backup. This is why I
decidedto go with non-exclusive to be ready when exclusive backup mode is finally removed some day. Yet, I don't see
thereason. Everything has to be consistent. So a non-exclusive backup mode makes absolutely no sense to me. Either the
wholedatabase cluster is in backup mode or it is not. There's nothing in between.
Glad that you went with the non-exclusive method.
When it comes to 'backup mode', it's actually the case that there can be
multiple backups running concurrently because there isn't actually a
single 'cluster wide backup mode', really. Regarding the deprecated
methodology, there just isn't a way for the database on-disk image to
look exactly like a backup while also being able to survive a
crash/restart with only the WAL that's in the pg_wal directory. Perhaps
there's other things we could do but at some point it has to be accepted
that there's gotta be something changed in the data directory to
indicate that it's a backup and not just a crash, and that change needs
to happen *after* the backup/snapshot/whatever has been taken, otherwise
there's a window of risk where a crash/restart would fail.
Thanks,
Stephen