Re: Any objections/comments on axing out old ATA stack?

On Sun, Mar 31, 2013 at 03:02:09PM -0600, Scott Long wrote:
> =

> On Mar 31, 2013, at 7:04 AM, Victor Balada Diaz <victor@bsdes.net> wrote:
> =

> > On Wed, Mar 27, 2013 at 11:22:14PM +0200, Alexander Motin wrote:
> >> Hi.
> >> =

> >> Since FreeBSD 9.0 we are successfully running on the new CAM-based ATA =

> >> stack, using only some controller drivers of old ata(4) by having =

> >> `options ATA_CAM` enabled in all kernels by default. I have a wish to =

> >> drop non-ATA_CAM ata(4) code, unused since that time from the head =

> >> branch to allow further ATA code cleanup.
> >> =

> >> Does any one here still uses legacy ATA stack (kernel explicitly built =

> >> without `options ATA_CAM`) for some reason, for example as workaround =

> >> for some regression? Does anybody have good ideas why we should not dr=
op =

> >> it now?
> > =

> > Hello,
> > =

> > At my previous job we had troubles with NCQ on some controllers. It cau=
sed
> > failures and silent data corruption. As old ata code didn't use NCQ we =
just used
> > it.
> > =

> > I reported some of the problems on 8.2[1] but the problem existed with =
8.3.
> > =

> > I no longer have access to those systems, so i don't know if the problem
> > still exists or have been fixed on newer versions.
> > =

> > Regards.
> > Victor.
> =

> =

> So what I hear you and Matthias saying, I believe, is that it should be e=
asier to
> force disks to fall back to non-NCQ mode, and/or have a more responsive
> black-list for problematic controllers.  Would this help the situation?  =
It's hard to
> justify holding back overall forward progress because of some bad control=
lers;
> we do several Tbps off of AHCI controllers with NCQ enabled on FreeBSD 9.=
x,
> enough to make up a sizable percentage of the internet's traffic, and we =
see no
> problems.  How can we move forward but also take care of you guys with
> problematic hardware?
> =

> Scott

Being able to configure quirks from loader.conf for disks AND controllers w=
ould be great
and is not hard to do. If you want i can do a patch in two weeks and send i=
t to you. That
way it's easy to test disabling NCQ and/or other things in case of hitting =
a bug. Also
being able to modify the configuration without a kernel recompile would be =
a big
improvement because we could still use freebsd-update to keep systems updat=
ed.

Anyway, my comment was not against dropping old ata code, but more on the "=
comments on
regresssions on the new one".

Regards.
Victor.
-- =

La prueba m=E1s fehaciente de que existe vida inteligente en otros
planetas, es que no han intentado contactar con nosotros. =

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