Re: Non-simultaneous file system snapshots as backups

Magnus Hagander wrote:
> On Fri, Mar 11, 2011 at 17:46, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> > I know we allow people to use file system snapshots as backups, but what
> > happens if they are using tablespaces and they can't do the snapshots
> > simultaneously? ?If there is only one check point happening between the
> > first and last snapshot, would the WAL logs clean up that inconsistency
> > like they do for crashes? ?I assume the pg_xlog directory would have to
> > be the last file system snapshotted. ?If so, is this something we should
> > document?
>
> If you can't take an atomic snapshot, you have to use
> pg_start_backup/pg_stop_backup. But as long as you do that, it works
> fine with any kind of snapshots. I don't think it's doable any other
> way.
>
> That said, there are systems that let you snapshot atomically across
> multiple tablespaces. But they tend to not be cheap.

Agreed, thanks.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +