Subject: Re: Bad performance, biowait on raid device
To: None <>
From: Manuel Bouyer <>
List: tech-kern
Date: 03/14/2006 20:07:09
On Tue, Mar 14, 2006 at 06:23:43PM +0100, wrote:
> On Tue, Mar 14, 2006 at 06:09:51PM +0100, Stefan Wurstbauer wrote:
> >  
> > I'm running NetBSD 3.0 on a Dell PowerEdge 4600 server. The disks are
> > 4 scsi disks / raid 5 on a hardware raid controller, mounted as a ffs
> > filesystem (without softdeps). 
> Without softdeps, the filesystem is operating in synchronised mode,
> meaning that almost all operations are serialised. Compare that with
> softdep or async mounts, where most operations are done in parallel and
> send as batch to the controller.

In addidtion, it depends if your hardware controller has battery-backed cache
or not. If it has a battery-backed cache, it can cache write requests,
and this can help a lot for file creations/deletions.

Manuel Bouyer <>
     NetBSD: 26 ans d'experience feront toujours la difference