Re: Best OS & Configuration for Dual Xeon w/4GB & Adaptec RAID 2200S

On Mar 17, 2006, at 5:11 PM, Kenji Morishige wrote:

> In summary, my questions:
>
> 1. Would running PG on FreeBSD 5.x or 6.x or Linux improve
> performance?

FreeBSD 6.x will definitely get you improvements. Many speedup
improvements have been made to both the generic disk layer and the
specific drivers. However, the current best of breed RAID controller
is the LSI 320-x (I use 320-2X). I have one box into which this
card will not fit (Thanks Sun, for making a box with only low-profile
slots!) so I use an Adaptec 2230SLP card in it. Testing shows it is
about 80% speed of a LSI 320-2x on sequential workload (load DB, run
some queries, rebuild indexes, etc.)

If you do put on FreeBSD 6, I'd love to see the output of "diskinfo -
v -t" on your RAID volume(s).

>
> 2. Should I change SCSI controller config to use RAID 10 instead of 5?

I use RAID10.

>
> 3. Why isn't postgres using all 4GB of ram for at least caching
> table for reads?

I think FreeBSD has a hard upper limit on the total ram it will use
for disk cache. I haven't been able to get reliable, irrefutable,
answers about it, though.

>
> 4. Are there any other settings in the conf file I could try to tweak?

I like to bump up the checkpoint segments to 256.