Re: Optimization questions

On Wed, Mar 13, 2002 at 05:23:30PM -0800, Gill, Jeffrey L wrote:
> Specs: Server RedHat 7.1 2.4.2-2 kernal everything build with Interchange
> 4.8
>
> I am learning Linux and Postgresql from scratch.
>
> 1. Can someone point me to or explain any linux kernal optimizations for
> redhat that can made to maximize performance of a postgresql server? I
> have briefly looked at Momjian's performance recommendations for the
> postgresql database itself, but I wondering if there is more that can be
> done?

A few kernel-parameters that could influence postgresql performance:
* VM code and settings. Kernels to try:
* Redhat 2.4.2
* newest Redhat kernel (2.4.9 based?)
* newest standard kernel, perhaps with aa and/or rmap patches.
(Don't know which is better, but a lot of changes have been made,
so the effect could be significant (one way or the other))
* Elevator settings (play with elvtune)
* Filesystems - my guess is that XFS is going to be the faster
filesystem for a postgresql database, but reiserfs may be able to
compete.

> 2. What RAID levels does postgresql support? I don't want to make any
> assumptions. I plan to put the data on an EMC Clariion FC4700 with RAID
> 10 eventually.

RAID-level 10 is probably the best general purpose RAID-level, as it
doesn't have the overhead of checksums that RAID5 has. However, if your
application is read intencive the difference may be neglectable. With
Raid 5 you don't need that many disks, so it will get you a cheeper
system.

If you want even better performance you should replace the Clariion with
a BigStorage T-RAID :)

> 4. How is Symmetric Multiprocessing Processor (SMP) configured? Can
> postgresql take advantage of SMP?

The kernel needs to be compiled with SMP support. The -smp and
-enterprise kernels from RedHat has SMP support built in - you should
use the enterprise version because it is better tuned for a big server.

--
Ragnar Kjorstad
Zet.no