Re: PITR, checkpoint, and local relations

> -----Original Message-----
> From: Tom Lane [mailto:tgl@sss.pgh.pa.us]
> Sent: Friday, August 02, 2002 4:02 PM
> To: J. R. Nield
> Cc: Richard Tucker; Bruce Momjian; PostgreSQL Hacker
> Subject: Re: [HACKERS] PITR, checkpoint, and local relations
>
>
> "J. R. Nield" <jrnield@usol.com> writes:
> > The predicate for files we MUST (fuzzy) copy is:
> >   File exists at start of backup && File exists at end of backup
>
> Right, which seems to me to negate all these claims about needing a
> (horribly messy) way to read uncommitted system catalog entries, do
> blind reads, etc.  What's wrong with just exec'ing tar after having
> done a checkpoint?
You do need to make sure to backup the pg_xlog directory last and you need
to make sure no wal file gets reused while backing up everything else.
>
> (In particular, I *strongly* object to using the buffer manager at all
> for reading files for backup.  That's pretty much guaranteed to blow out
> buffer cache.  Use plain OS-level file reads.  An OS directory search
> will do fine for finding what you need to read, too.)
>
>             regards, tom lane
>