Re: PITR, checkpoint, and local relations

Maybe we don't have to turn off checkpointing but we DO have to make sure no
wal files get re-used while the backup is running.  The wal-files must be
archived after everything else has been archived.  Futhermore if we don't
stop checkpointing then care must be taken to backup the pg_control file
first.
-regards
richt

> -----Original Message-----
> From: Tom Lane [mailto:tgl@sss.pgh.pa.us]
> Sent: Friday, August 02, 2002 7:49 PM
> To: richt@multera.com
> Cc: Mikheev, Vadim; J. R. Nield; Bruce Momjian; PostgreSQL Hacker
> Subject: Re: [HACKERS] PITR, checkpoint, and local relations
>
>
> Richard Tucker <richt@multera.com> writes:
> > 1) Issue an ALTER SYSTEM BEGIN BACKUP command which turns on
> atomic write,
> > checkpoints the database and disables further checkpoints (so wal files
> > won't be reused) until the backup is complete.
> > 2) Change ALTER SYSTEM BACKUP DATABASE TO <directory> read the database
> > directory to find which files it should backup rather than
> pg_class and for
> > each file just use system(cp...) to copy it to the backup directory.
> > 3) ALTER SYSTEM FINISH BACKUP does at it does now and backs up
> the pg_xlog
> > directory and renables database checkpointing.
>
> > Does this sound right?
>
> I really dislike the notion of turning off checkpointing.  What if the
> backup process dies or gets stuck (eg, it's waiting for some operator to
> change a tape, but the operator has gone to lunch)?  IMHO, backup
> systems that depend on breaking the system's normal operational behavior
> are broken.  It should be sufficient to force a checkpoint when you
> start and when you're done --- altering normal operation in between is
> a bad design.
>
>             regards, tom lane
>