Re: Re: Synch Rep: direct transfer of WAL file from the primary to the standby

Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> And I'm sure people will want the option to retain WAL longer in the
> master, to avoid an expensive resync if the slave falls behind. It would
> be simple to provide a GUC option for "always retain X GB of old WAL in
> pg_xlog".

Right, we would want to provide some more configurability on the
when-to-recycle-WAL decision than there is now. But the basic point
is that I don't see the master pg_xlog as being a long-term archive.
The amount of back WAL that you'd want to keep there is measured in
minutes or hours, not weeks or months.

(If nothing else, there is no point in keeping so much WAL that catching
up by scanning it would take longer than taking a fresh base backup.
My impression from recent complaints about our WAL-reading speed is that
that might be a pretty tight threshold ...)

regards, tom lane