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From: Anton Ertl on 9 Dec 2006 09:59
We recently got a server based on the SuperMicro X7DBE+ board, i.e.,
the Intel 5000P chipset, with SATA disk I/O done by the ESB2 chip. In
the BIOS we can set Legacy mode (the default), or AHCI mode. From
what I read on <http://linuxmafia.com/faq/Hardware/sata.html>, AHCI
has a number of advantages, like NCQ (not sure if that is supported by
the driver yet), so we selected that.

We then tried to install 64-bit Debian etch on the box using the
Debian net-install CD. This worked fine for a time, but while
installing additional packages, it hung at an installation step (not
in the download). I could get it to continue by killing (with -9) the
hanging process (but I guess that the install is not complete; the
installer reported an error and I repeated the step, but my impression
is that this package was not installed again).

Later it hung repeatably while installing Grub, and I got around that
by terminating the parent of the hanging process (the hanging process
was in the D state (uninterruptible sleep). Also, "sync" seemed to
take very long (a few minutes). Other shell commands worked fine, so
I doubt that the hangs have to do with the power-saving states that we
enabled in the BIOS.

Instead, since the hangs happened on disk accesses, I suspect and that
they have to do with the disk driver. A theory my collegue has is
that the disc syncing that the md driver was doing at the time was the
culprit, but I doubt this (in my experience md syncing is very
unobstrusive).

I looked in the logs, but found no suspicious kernel message there.

So, the next step would be to go into legacy mode and try again, but
if you have a better suggestion, let me know.

Hmm, since all the file systems are on md devices, switching later
from legacy mode (where the disks are /dev/hd* AFAIK) to AHCI mode
(where the disks are /dev/sd*) should be relatively painless.

- anton
--
M. Anton Ertl Some things have to be seen to be believed
anton(a)mips.complang.tuwien.ac.at Most things have to be believed to be seen
http://www.complang.tuwien.ac.at/anton/home.html
From: Anton Ertl on 13 Dec 2006 13:46
anton(a)mips.complang.tuwien.ac.at (Anton Ertl) writes:
[process hangs on installing Debian etch]
>Instead, since the hangs happened on disk accesses, I suspect and that
>they have to do with the disk driver. A theory my collegue has is
>that the disc syncing that the md driver was doing at the time was the
>culprit, but I doubt this (in my experience md syncing is very
>unobstrusive).

We just repeated that part of the installation (very little work
repeated), and it did not hang while installing a package, but
appeared to hang when installing Grub. But eventually that part
completed (lunch made me patient:-). Maybe the md syncing had to do
with it: when the Grub installation had completed, the md syncs were
completed, too.

The machine appears to work fine now.

Sorry, no real resolution, just some update in case one of you hits on
a similar problem.

- anton
--
M. Anton Ertl Some things have to be seen to be believed
anton(a)mips.complang.tuwien.ac.at Most things have to be believed to be seen
http://www.complang.tuwien.ac.at/anton/home.html
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