ahci.ko in RELENG_8_2, what about atacontrol cap?

[Jeremy Chadwick]

On Sun, Apr 03, 2011 at 12:21:55PM +0200, Patrick M. Hausen wrote:
> Hello,
> 
> Am 02.04.2011 um 11:40 schrieb Jeremy Chadwick:
> > You want "camcontrol identify adaX".  DO NOT confuse this with
> > "camcontrol inquiry adaX" (this won't work).
> > 
> > identify = for ATA
> > inquiry  = for SCSI
> 
> Works perfectly, but I just noticed one really odd thing:
> 
> 1. boot without ahci.ko:
> 
> nas-pmh# atacontrol cap ad4
> ...
> write cache                    yes	yes
> 
> 
> 2. boot with ahci.ko:
> 
> nas-pmh# camcontrol identify ada0
> ...
> write cache                    yes	no
> 
> 
> Well? ;-) The system is a HP NL36 - I just found a couple
> of articles mentioning that the default setting in the BIOS
> setup was write cache disabled. I can check that in the
> next couple of days when I take the machine back to the
> lab (no monitor/keyboard at my home office).
> 
> I'd prefer a way to make sure write cache is enabled via
> some tuning from FreeBSD. The disks are dedicated to
> a raidz2, so from what I found around the net, write cache
> should not pose a major problem. Of course, one will lose
> _some_ data at a power outage - what I want to avoid
> for home office use is a completely lost file system.
> Losing the last time machine backup of my Mac is tolerable.

I don't have an explanation for what you're seeing.  I can't reproduce
it on any of our Supermicro systems (ICH9R-based, backed by a multitude
of disk types; Intel X25-M and X25-V SSDs, WD Caviar Black 750GB, 1TB,
and 2TB, etc.).

CC'ing mav@ who might have some ideas.  I don't see anything in RELENG_8
that looks relevant (just went through src/sys/dev/ahci's commit log).

Alexander, disk type is here (Seagate ST32000542AS):
http://lists.freebsd.org/pipermail/freebsd-stable/2011-April/062142.html

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.               PGP 4BD6C0CB |