On Thu, Dec 16, 2004 at 04:10:39PM -0800, Bill Studenmund wrote:
> [...]
> > The thing I liked about the completion queue idea is that it stays
> > etirely within the disk driver layer, and merely restores the disk
> > semantics that are assumed by all the upper layers: biodone buffers
> > are safely on stable storage. 
> 
> But those semantics are not always the right ones for the upper levels.
> Yes, those are the ones everything grew up with. But write-back caches    
> were added to disks (and enabled by default) for a reason - they let the
> disk perform very well. Other OSs cope well with this. If we want to
> perform well, we will need to as well.
> 
> I agree it's wrong to assume we don't have write caches when we do, but I 
> think you tackle the problem backwards. Rather than hide the write caches, 
> I think we need to start changing the upper code to deal with them.

What he said.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--