Re: Inserting 8MB bytea: just 25% of disk perf used?

Scott Carey wrote:
>> #bgwriter_delay=200ms
>> #bgwriter_lru_percent=1.0
>> #bgwriter_lru_maxpages=5
>> #bgwriter_all_percent=0.333
>> #bgwriter_all_maxpages=5
>> #checkpoint_segments=3
>> #checkpoint_timeout=5min
>> #checkpoint_warning=30s
>>
>
> Check out this for info on these parameters
> http://wiki.postgresql.org/wiki/User:Gsmith (Is there a better link Greg?)
>

Nope. I started working on that back when I had some hope that it was
possible to improve the background writer in PostgreSQL 8.2 without
completely gutting it and starting over. The 8.3 development work
proved that idea was mistaken, which meant historical trivia about how
the ineffective 8.2 version worked wasn't worth cleaning up to
presentation quality anymore. Stuck it on my personal page on the wiki
just so I didn't lose it and could point at it, never developed into a
proper article.

Generally, my advice for people running 8.2 is to turn the background
writer off altogether:

bgwriter_lru_maxpages=0
bgwriter_all_maxpages=0

Because what is there by default isn't enough to really work, and if you
crank it up enough to do something useful it will waste a lot
resources. It's possible with careful study to find a useful middle
ground--I know Kevin Grittner accomplished that on their 8.2 install,
and I did it once in a way that wasn't horrible--but you're unlikely to
just get one easily.

--
Greg Smith 2ndQuadrant Baltimore, MD
PostgreSQL Training, Services and Support
greg(at)2ndQuadrant(dot)com www.2ndQuadrant.com