From: | Richard Tucker <richt(at)multera(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | "Mikheev, Vadim" <vmikheev(at)SECTORBASE(dot)COM>, "J(dot) R(dot) Nield" <jrnield(at)usol(dot)com>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, PostgreSQL Hacker <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: PITR, checkpoint, and local relations |
Date: | 2002-08-07 15:01:59 |
Message-ID: | EKEKLEKKLDAEEKDBDMMAKEJGCDAA.richt@multera.com |
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Lists: | pgsql-hackers |
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archived after everything else has been archived.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(at)sss(dot)pgh(dot)pa(dot)us]
> Sent: Friday, August 02, 2002 7:49 PM
> To: richt(at)multera(dot)com
> Cc: Mikheev, Vadim; J. R. Nield; Bruce Momjian; PostgreSQL Hacker
> Subject: Re: [HACKERS] PITR, checkpoint, and local relations
>
>
> Richard Tucker <richt(at)multera(dot)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
>
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