Re: Performance tuning on FreeBSD

On Mon, Mar 3, 2008 at 5:11 PM, Greg Smith <gsmith(at)gregsmith(dot)com> wrote:
> On Mon, 3 Mar 2008, alan bryan wrote:
>
> >> pgbench -c 100 -t 1000 testdb
>
> > tps = 558.013714 (excluding connections establishing)
> >
> > Just for testing, I tried turning off fsync and got:
>
> > tps = 4061.662041 (excluding connections establishing)
>
> This is odd. ~500 is what I expect from this test when there is no write
> cache to accelerate fsync, while ~4000 is normal for your class of
> hardware when you have such a cache. Since you say your 3Ware card is
> setup with a cache and a BBU, that's suspicious--you should be able to get
> around 4000 with fsync on. Any chance you have the card set to
> write-through instead of write-back? That's the only thing that comes to
> mind that would cause this.
>
> --
> * Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD
>

According to 3dm2 the cache is on. I even tried setting The StorSave
preference to "Performance" with no real benefit. There seems to be
something really wrong with disk performance. Here's the results from
bonnie:

File './Bonnie.2551', size: 104857600
Writing with putc()...done
Rewriting...done
Writing intelligently...done
Reading with getc()...done
Reading intelligently...done
Seeker 1...Seeker 2...Seeker 3...start 'em...done...done...done...
-------Sequential Output-------- ---Sequential Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
100 9989 4.8 6739 1.0 18900 7.8 225973 98.5 1914662
99.9 177210.7 259.7

This is on FreeBSD 7.0-Release. I tried ULE and 4BSD schedulers with
no difference. Maybe I'll try FreeBSD 6.3 to see what that does?