Subject: Re: RAID tuning
To: Greg Oster <firstname.lastname@example.org>
From: Jukka Marin <email@example.com>
Date: 12/19/2002 23:29:14
On Thu, Dec 19, 2002 at 03:20:02PM -0600, Greg Oster wrote:
> > Why is raid 94.4% busy when the components (wd0, wd1) are only 3%
> > busy? CPU is about 90% idle.
> Not sure.
The RAID feels slow although the disks are fast and I can read over 30 MB/s
from both disks simultaneously IIRC (without RAID).
> > Someone said I should be using "scan" instead of "fifo" with IDE disks.
> > Why is that?
> I'd ask the "someone" ;)
I did. I'm still waiting. :) It just happens that I'm playing with this
server box now (with the bufcache setting) and wanted to tune RAID as well.
> > Can I change this parameter without initializing the raid
> > set (ie. losing all my data)?
> Yes. Note that the queue type (and size) is not stored in the component
> labels, so if you're using autoconfig, then it will automatically use fifo,
> and you won't be able to change it. (yes, that's a bug, and yes, it's on my
> TODO list, and no, there hasn't been a lot (read: any) demand to fix that
> bug yet :-} )
Aa. I'm using autoconfig because I boot from RAID. So _that_ is why I
didn't see any difference when I benchmarked the RAID with "fifo" and