Re: Tuning PostgreSQL

On 2003-07-21 09:06:10 -0700, Josh Berkus wrote:
> Alexander,
>
> > Hmmm. Seems to me that this setup would be better than one RAID5 with three
> > 36Gb disks, wouldn't you think so? With one RAID5 array, I would still have
> > the data and the WAL on one volume...
>
> Definitely. As I've said, my experience with RAID5 is that with less than 5
> disks, it performs around 40% of a single scsi disk for large read-write
> operation on Postgres.
>
> If you have only 3 disks, I'd advocate one disk for WAL and one RAID 1 array
> for the database.
>

In this setup your database is still screwed if a single disk (the WAL disk)
stops working. You'll have to revert to your last backup if this happens. The
RAID-1 redundancy on your data disks buys you almost nothing: marginally
better performance and no real redundancy should a single disk fail.

I'd use RAID-5 if you absolutely cannot use more disks, but I would use
RAID-10 or two RAID-1 partitions if you can afford to use 4 disks.

Vincent van Leeuwen
Media Design - http://www.mediadesign.nl/