Subject: Re: Limiting disk I/O?
To: None <>
From: Joerg Sonnenberger <>
List: tech-kern
Date: 11/13/2007 16:05:40
On Tue, Nov 13, 2007 at 09:36:22AM +0200, Jukka Marin wrote:
> 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.

In that case the driver can do that completely internal.