On Wed, Mar 6, 2013 at 8:17 PM, Greg Smith <greg@2ndquadrant.com> wrote:
> TL;DR summary: on a system I thought was a fair middle of the road server,
> pgbench tests are averaging about a 2% increase in WAL writes and a 2%
> slowdown when I turn on checksums. There are a small number of troublesome
> cases where that overhead rises to closer to 20%, an upper limit that's
> shown up in a few tests aiming to stress this feature now.
I have only done some cursory research, but cpu-time of 20% seem to
expected for InnoDB's CRC computation[0]. Although a galling number,
this comparison with other systems may be a way to see how much of
that overhead is avoidable or just the price of entry. It's unclear
how this 20% cpu-time compares to your above whole-system results, but
it's enough to suggest that nothing comes for (nearly) free.
[0]: http://mysqlha.blogspot.com/2009/05/innodb-checksum-performance.html
--
fdr