Subject: Re: FFSv1 performance on large filesystems
To: Matthias Scheler <tron@zhadum.de>
From: Chris Gilbert <chris@dokein.co.uk>
List: tech-perform
Date: 03/04/2005 00:25:08
On Thu, 3 Mar 2005 22:46:44 +0000
Matthias Scheler <tron@zhadum.de> wrote:

> On Thu, Mar 03, 2005 at 09:48:06PM +0000, Chris Gilbert wrote:
> > Looking at the above, both disks on the same PATA channel?
> 
> Yes.
> 
> > Have you tried having each disk on it's own PATA channel?
> 
> No. The machine has four PATA disks and only two PATA channels which means
> that I cannot avoid sharing. I arranged the disks as they are now (raid0
> on wd0 and wd1, raid1 on wd2 and wd3) to avoid performance hits on raid0
> when raid1 (which e.g. contains my NetBSD source trees) is very busy.

Might be worth a try, but have you considered moving things around a bit, eg:

currently:
Channel 0: raid0 disk 1 and raid0 disk 2
Channel 1: raid1 disk 1 and raid1 disk 2

and try:
Channel 0: raid0 disk 1 and raid1 disk 1
Channel 1: raid0 disk 2 and raid1 disk 2

that means that access to both disks in raid0 can be used together, as can both disks in raid1, which might speed things up?  Obviously performance to both raid0 and raid1 together may suck, but perhaps no worse than currently?

Chris