Subject: Re: disks write-back cache
To: Patrick Welche <>
From: Manuel Bouyer <>
List: tech-kern
Date: 04/29/2003 20:55:48
On Tue, Apr 29, 2003 at 09:31:54AM +0100, Patrick Welche wrote:
> I just replace the kernel with an old one, and have done another
> 3 successful make releases on that machine, so I really can't
> believe it's the disks which are at fault.. (With a new kernel
> the disklabel of one of the disks was even changed(!)) The best
> I can think of is that maybe the new ahc driver reorders commands
> more agressively? Is it possible? Does it expect the "yes I've
> written it" from the disk to be true?

No, the driver itself shouldn't reorder the commands. The drive may.

> Anyway, I'll try switching off write-back to see if that improves
> things, and then try switching off tagged queueing.

This would be a good test. I played a bit on sparc64, with 2
disks connected and couldn't reproduce the problem. But I only have a
plain 2940UW, which also worked fine with the old driver.

> I'm assuming
> it's safe to install a new fsck binary with an old (16th April)
> kernel to help patch up the disks after they have been messed up
> by the new kernel..

It should.

Manuel Bouyer <>
     NetBSD: 24 ans d'experience feront toujours la difference