Subject: Re: RAID tuning
To: Greg Oster <>
From: Jukka Marin <>
List: netbsd-users
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
"scan" ;-)