On Tue, 6 Dec 2005, Thomas Harold wrote:
Ron wrote:
For accuracy's sake, which exact config did you finally use?
How did you choose the config you finally used? Did you test the three
options or just pick one?
(Note: I'm not the original poster.)
I just picked the option of putting the data/pg_xlog directory (WAL) on a 2nd
set of spindles. That was the easiest thing for me to change on this test
box.
The test server is simply a Gentoo box running software RAID and LVM2. The
primary disk set is 2x7200RPM 300GB drives and the secondary disk set is
2x5400RPM 300GB drives. Brand new install of PGSQL 8.1, with mostly default
settings (I changed FSM pages to be a higher value, max_fsm_pages = 150000).
PGSQL was given it's own ext3 32GB LVM volume on the primary disk set
(2x7200RPM). Originally, all files were on the primary disk.
the WAL is more sensitive to drive speeds then the data is, so you may
pick up a little more performance by switching the WAL to the 7200 rpm
drives instead of the 5400 rpm drives.
if you see a noticable difference with this, consider buying a pair of
smaller, but faster drives (10k or 15k rpm drives, or a solid-state
drive). you can test this (with significant data risk) by putting the WAL
on a ramdisk and see what your performance looks like.
David Lang
