Re: Non-simultaneous file system snapshots as backups

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.

--
 Magnus Hagander
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