Re: more 10K disks or less 15K disks

On Thu, Apr 29, 2010 at 11:26 AM, Anj Adu <fotographs(at)gmail(dot)com> wrote:
> All the disks are usually laid out in a single RAID 10 stripe . There
> are no dedicated disks for the OS/WAL as storage is a premium

You should at least investigate the performance difference of having a
separate volume for WAL files on your system. Since WAL files are
mostly sequential, and db access is generally random, the WAL files
can run really quickly on a volume that does nothing else but handle
WAL writes sequentially. Given the volume you're handling, I would
expect that storage is not any more important than performance.

The fact that you're asking whether to go with 12 or 24 600G disks
shows that you're willing to give up a little storage for performance.
I would bet that the 24 10k disks with one pair dedicated for OS /
pg_xlog would be noticeably faster than any single large volume config
you'd care to test, especially for lots of active connections.