problems with AHCI on FreeBSD 8.2

Jeremy Chadwick freebsd at
Wed Feb 15 10:42:09 UTC 2012

On Wed, Feb 15, 2012 at 10:19:37AM +0000, Tom Evans wrote:
> On Tue, Feb 14, 2012 at 7:52 PM, Jeremy Chadwick
> <freebsd at> wrote:
> > On Tue, Feb 14, 2012 at 08:31:23PM +0100, Oscar Prieto wrote:
> >> I used to had tons of ahci errors in my 4 disk raidz1 worth of
> >> HD154UIs when the rig was built a year ago or so (with 8.0 Release),
> >> but they dissapeared after tuning ZFS.
> >>
> >> Sadly i also got a new timeout days ago followed with smartcl erros i
> >> still keep unchecked but i guess they cold be legit, i still have to
> >> test/swap cables and give it a try.
> Interesting. I have 9 SAMSUNG HD154UI 1AG01118 in my raidz setup,
> haven't had a problem with any of them yet (touch wood).
> > Further details which pertain to Samsung drives:
> >
> > In your case, you run smartd(8), which periodically hits the drive with
> > SMART requests, pulling attribute data down and parsing it. ??I believe
> > your model is fine for this, but for similar Samsung models, I must
> > strongly advise against this. ??There are well-documented problems with
> > Samsung firmwares and SMART behaviour which can result in data loss (yes
> > you read that right). ??Please see smartmontools' Wiki page on the matter
> > for full details. ??Just make sure you're running a fixed firmware:
> >
> >
> >
> Yikes, I have just this week installed a HD204UI. From that page,
> drives manufactured after December 2010 should not be affected, which
> is fortunate as the linked firmware page doesn't seem to exist
> anymore, Samsung no longer seem to offer support for their drives and
> point you at Seagate, whose site (of course!) only has downloads for
> current Seagate drives.
> Hmm reading later on in the thread there is a patch to mark certain
> drives as having flaky NCQ - in the patch it is for the SAMSUNG
> HD154UI. As I mentioned before, I have 9 SAMSUNG HD154UI, all of which
> use ahci(4) and NCQ, and all work perfectly, no timeouts. This is
> using 9-STABLE.
> I suspect that there may be more going on than 'flaky NCQ', and that
> perhaps disabling NCQ masks the real issue.

It could simply be a firmware bug in the drive, which is what some
others have eluded to (and I'm in agreement with).  I would love to say
"compare firmware versions on your drives", except there is real
in-the-field proof that firmware version strings often do not get
updated/changed between firmwares (at least in the case of some Seagate
and Western Digital disks).  Furthermore, NCQ can "play differently" with
different AHCI controllers.

That said, the disks / firmware versions mentioned by people involved in
this thread / referenced threads are:

* Victor Balada Diaz  -- SAMSUNG HD154UI, firmware 1AG01118
* Claudius Herder     -- SAMSUNG HD753LJ, firmware 1AA01118
* Oscar Prieto        -- SAMSUNG HD154UI, firmware 1AG01118
  - NOTE: In Oscar's case, his drives exhibit other problems.  I
    would provide a link but the web archive for freebsd-stable does
    not show my mail which contains analysis of the situation
* Harald Schmalzbauer -- not provided, but hints at Samsung EG drives

For this to be thorough, one would need to check what all AHCI
controllers are being used and compare those as well.

I think Scott's theory is probably on-the-ball here, as it pertains to
tag exhaustion, which would manifest itself in the described fashion:

I'd urge people experiencing this problem to issue the command Scott
provided on all their Samsung disks and see if the problem goes away
after that.  If it does, great, and I acknowledge there is no
loader.conf tunable for doing this, etc. etc. etc. so either make an
rc.d script that does it after boot-up or something.

| Jeremy Chadwick                              jdc at |
| Parodius Networking            |
| UNIX Systems Administrator                 Mountain View, CA, US |
| Making life hard for others since 1977.             PGP 4BD6C0CB |

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