Simon Riggs <simon@2ndQuadrant.com> wrote:
> [most significant extra WAL logging for hot standby is:]
> * one extra WAL record every checkpoint, containing a full current
> snapshot's worth of running xids 100-400 bytes typically, could go
> up from there to 4000 bytes in very extreme write workloads that
> also have many, many subtransactions
The most convincing evidence that there's no significant performance
hit for those not needing the feature (and not a bad thing from a
testing point of view anyway) would be for someone to run some
benchmarks comparing the archive and hot_standby logging levels,
with no archive script or SR. If that hasn't been done yet, maybe
you could find somebody who knows his way around pgbench-tools, who
could construct a reasonable test and produce graphs and all that
cool stuff. ;-) IMO, isolating the cost of generating and writing
the extra WAL would be very valuable, and it would be reassuring to
know that it worked with a large number of clients without exposing
any dire race conditions.
-Kevin