Re: online tape backup

Michael Monnerie <michael(dot)monnerie(at)it-management(dot)at> writes:
> On Dienstag, 13. Februar 2007 16:34 Tom Lane wrote:
>> You're suffering from a fundamental misconception about the nature of
>> WAL. Vacuum doesn't "shrink WAL", and neither does anything else;

> Seems you didn't understand me: When I make a vacuum, and then a base
> backup, I do not need to include the WAL records anymore. But when I do
> a base backup and afterwards vacuum, the WAL will be huge already, also
> making restore much longer.

This is irrelevant, at least in a steady-state environment. If you
vacuum beforehand, the WAL history for that has to be included in what
you need to recover from your previous base backup; and you can't
discard that data until after you take the new backup. So AFAICS it's a
wash; the average time-to-recover is the same either way. Or at least,
VACUUM is not any different from any other burst of activity that you
might want to schedule around.

regards, tom lane