From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | richt(at)multera(dot)com |
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: | 2002-08-02 23:49:07 |
Message-ID: | 29010.1028332147@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
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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