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

Jeffrey W. Baker wrote:
> On Tue, 2005-08-16 at 10:46 -0700, Roger Hand wrote:
>> The disks are ext3 with journalling type of ordered, but this was later changed to writeback with no apparent change in speed.
>>
>> They're on a Dell poweredge 6650 with LSI raid card, setup as follows:
>> 4 disks raid 10 for indexes (145GB) - sdc1
>> 6 disks raid 10 for data (220GB) - sdd1
>> 2 mirrored disks for logs - sdb1
>>
>> stripe size is 32k
>> cache policy: cached io (am told the controller has bbu)
>> write policy: write-back
>> read policy: readahead
>
> I assume you are using Linux 2.6.

Oops, sorry I left that out. Nope, we're on 2.4:

[root(at)rage-db2 ~]$ uname -a
Linux xxx.xxx.xxx 2.4.21-27.0.2.ELsmp #1 SMP Wed Jan 12 23:35:44 EST 2005 i686 i686 i386 GNU/Linux

It's RedHat Enterprise AS3.0 Fri Nov 5 17:55:14 PST 2004

> Have you considered booting your
> machine with elevator=deadline?

I just did a little Googling and see that the 2.4 kernel didn't have a decent elevator tuning system, and that was fixed in 2.6. Hmmm ....

Thanks for the ideas ...

-Roger