Subject: Re: Limiting disk I/O?
To: Michael van Elst <>
From: Jukka Marin <>
List: tech-kern
Date: 11/13/2007 09:36:22
On Tue, Nov 13, 2007 at 07:15:15AM +0000, Michael van Elst wrote:
> >Wouldn't it be simpler to implement a new sysctl'able variable to limit the
> >tps to some percentage of the disk I/O capacity?
> The problem is not the disk. If you slow down the disk artificially
> you just make the problem larger as you run out of buffers earlier.

The disk is part of the problem, at least with twa.  It seems the performance
collapses when the controller becomes real busy.  Even tw_cli (the 3ware cli
tool) starts to crawl when softdep is pushing data to disk.