Re: 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