Subject: Re: disks write-back cache
To: Manuel Bouyer <>
From: Patrick Welche <>
List: tech-kern
Date: 05/01/2003 22:41:13
On Tue, Apr 29, 2003 at 08:55:48PM +0200, Manuel Bouyer wrote:
> 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.

And switching off write-back cache so far seems to have cured things..

The story is:

ahc  write-back cache      tagged queueing      state
old       enabled             enabled           rock solid 24/7
new       enabled             enabled           creates corrupt files/fsck :(
new       disabled            enabled           make release succeeded

So was I just lucky before?