Re: Is full_page_writes=off safe in conjunction with PITR?

Jim C. Nasby wrote:
> On Mon, Apr 17, 2006 at 03:00:58PM -0400, Tom Lane wrote:
> > I've applied a patch for this.  On reflection, the CHECKPOINT during
> > pg_start_backup was actually necessary for torn-page safety even without
> > full_page_writes off.  The reason is that the torn-page risk occurs when
> > we write a page from shared memory, not when we modify it in memory.
> > Without a CHECKPOINT, a page modified just before pg_start_backup could
> > be dumped during the backup and then be saved in a torn state, even
> > though no WAL record for it is emitted anytime during the backup
> > procedure.  So that comment's been wrong all along.
> 
> Are you going to back-patch this? If I understand correctly current
> behavior could mean people using PITR may have invalid backups. In the
> meantime, perhaps we should send an email to -annouce recommending that
> folks issue a CHEKCPOINT; after pg_start_backup and before initiating
> the filesystem copy.

We are disabling full_page_writes for 8.1.4, so they should be fine.


--  Bruce Momjian   http://candle.pha.pa.us EnterpriseDB    http://www.enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +