Subject: AW: Bad performance, biowait on raid device
To: None <tech-kern@NetBSD.org>
From: Stefan Wurstbauer <firstname.lastname@example.org>
Date: 03/14/2006 22:38:44
> On Tue, Mar 14, 2006 at 06:23:43PM +0100, email@example.com 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 >
> or not. If it has a battery-backed cache, it can cache write requests,
> and this can help a lot for file creations/deletions.
It has a battery-backed cache.
The reason why I switched off softdeps was a big problem during heavy IO
processes (backup). After running the box for a while (10-40 days) the