Re: Why is vacuum_freeze_min_age 100m?

"Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> (2) there's not really much to be gained by reducing it.

> That depends.  The backup techniques I recently posted, using hard
> links and rsync, saved us the expense of another ten or twenty TB of
> mirrored SAN archival storage space, and expensive WAN bandwidth
> upgrades.  In piloting this we found that we were sending our
> insert-only data over the wire twice -- once after it was inserted and
> once after it aged sufficiently to be frozen.  Aggressive freezing
> effectively cut our bandwidth and storage needs for backup down almost
> by half.  (Especially after we made sure we left enough time for the
> VACUUM FREEZE to complete before starting that night's backup
> process.)

Hmmm ... if you're using VACUUM FREEZE, its behavior is unaffected by
this GUC anyway --- that option makes it use a freeze age of zero.

            regards, tom lane