Re: Impact of checkpoint_segments under continual load conditions

On 7/18/05, Vivek Khera <vivek(at)khera(dot)org> wrote:
>
> On Jul 17, 2005, at 1:08 PM, Christopher Petrilli wrote:
>
> > Normally, checkpoint_segments can help absorb some of that, but my
> > experience is that if I crank the number up, it simply delays the
> > impact, and when it occurs, it takes a VERY long time (minutes) to
> > clear.
>
> There comes a point where your only recourse is to throw hardware at
> the problem. I would suspect that getting faster disks and splitting
> the checkpoint log to its own RAID partition would help you here.
> Adding more RAM while you're at it always does wonders for me :-)

My concern is less with absolute performance, than with the nosedive
it goes into. I published some of my earlier findings and comparisons
on my blog, but there's a graph here:

http://blog.amber.org/diagrams/comparison_mysql_pgsql.png

Notice the VERY steep drop off. I'm still trying to get rid of it,
but honestly, am not smart enough to know where it's originating. I
have no desire to ever use MySQL, but it is a reference point, and
since I don't particularly need transactional integrity, a valid
comparison.

Chris
--
| Christopher Petrilli
| petrilli(at)gmail(dot)com