Re: Ideal disk setup for Postgresql 7.4?

Steve,

> I help manage an animal hospital of 100-employees Linux servers. I am
> new to database setup and tuning, I was hoping I could get some
> direction on a setting up drive array we're considering moving our
> database to.

Check what I have to say at http://www.powerpostgresql.com/PerfList

> They're currently on a two-disk Adaptec RAID1 with Postgresql 7.4.2.

And you've not upgraded to 7.4.6 because .... ?

> The drive array is a 7-disk fibre channel on a Qlogic 2100 controller. I
> am currently testing RAID5 (sw).

In general, RAID 5 is not so great for databases. See the article for more.

> The main reason of moving to a drive array is the high level of context
> switches we get during the day (>30K for 20 mins per hour). The OS and
> database exist on the same disk but seperate parition (which probably
> makes little difference)

Unfortunately, the context switches are probably due to a known issue in
PostgreSQL, and changing the drive array won't help this issue (it may help
other issues though). Search the archives of this list, and pgsql-hackers,
for "Context Switch Bug".

For the CS bug, the only workaround right now is to avoid the query structures
that trigger it.

> Server Info:
> Centos 3.3 (RHEL 3.x equivelent)
> 4GB RAM
> Adaptec 2100S RAID
> Qlogic QLA2100 Fibre

CPU?

--
Josh Berkus
Aglio Database Solutions
San Francisco