Subject: Re: I/O priorities
To: Manuel Bouyer <bouyer@antioche.eu.org>
From: Rick Kelly <rmk@toad.rmkhome.com>
List: tech-kern
Date: 06/20/2002 15:35:00
Manuel Bouyer said:

>On Thu, Jun 20, 2002 at 12:09:44PM -0700, Greywolf wrote:

>> Why not prioritise by type of partition rather than by partition proper
>> (i.e. say swap gets slightly lower priority than ffs)?  Is there need to
>> prioritise by physical partition?

>Why limit to type of partitions, when you could have a finer-grain tuning ?
>I'd like to be able to say, on my mail server, / and /usr should be
>serviced before /var/mail, for example.

Swap really needs to have high priority for good performance.

Many people who are running UNIX on the desktop these days are using
an i386 box with one huge IDE disk.

The problem is that a box with one disk, no matter how fast it is, will
perform badly under high load. All my boxes that have to perform have
multiple SCSI disks with swap partitions on each disk, which much improves
swap performance. Also, I reserve sd0a as an OS only disk, and put users
and applications on partitions of the other disks.

My -current box is a P200MMX with 128 megs of memory. The system is spread
across 3 9gig disks. While I see the i/o problem, the box never really
becomes unuseable.
-- 
Rick Kelly  rmk@rmkhome.com  www.rmkhome.com