Re: Query plan looks OK, but slow I/O - settings advice?

On Aug 19, 2005, at 12:55 AM, Jeffrey W. Baker wrote:

> On Tue, 2005-08-16 at 10:46 -0700, Roger Hand wrote:
>   Have you considered booting your
> machine with elevator=deadline?

Although I'm not the OP for this problem, I thought I'd try it out.
WOW.. this should be in a Pg tuning guide somewhere. I added this to
my server tonight just for kicks and saw a pronounced improvement in
IO performance.  Thank you very much for mentioning this on the list.

I didn't have a long enough maintenance window to do solid
benchmarking, but I can say for certain that the change was
noticeable, especially in VACUUM operations.

Specs for the server:

PG 8.0.1
Linux 2.6.12-3 kernel
4xOpteron 2.2
12GB RAM
16-drive RAID 10
XFS mounted with noatime
pg_xlog on separate RAID controller

-Dan