disk "flipped" - a known problem?

[Jeremy Chadwick]

(Please keep me CC'd as I am not subscribed)

WRT this:

http://lists.freebsd.org/pipermail/freebsd-fs/2013-January/016197.html

I can reproduce the first problem 100% of the time on my home system
here.  I can provide hardware specs if needed, but the important part is
that I'm using RELENG_9 / r245697, the controller is an ICH9R in AHCI
mode (and does not share an IRQ), hot-swap bays are in use, and I'm
using ahci.ko.

I also want to make this clear to Andriy: I'm not saying "there's a
problem with your disk".  In my case, I KNOW there's a problem with the
disk (that's the entire point to my tests! :-) ).

In my case the disk is a WD Raptor (150GB, circa 2006) that has a very
badly-designed firmware that goes completely catatonic when encountering
certain sector-level conditions.  That's not the problem though -- the
problem is with FreeBSD apparently getting confused as to the internal
state of its devices after a device falls off the bus and comes back.
Explanation:

1. System powered off; disk is attached; system powered on, shows up as
ada5.  Can communicate with device in every way (the way I tend to test
simple I/O is to use "smartctl -a /dev/ada5").  This disk has no
filesystems or other "stuff" on it -- it's just a raw disk, so I believe
the g_wither_washer oddity does not apply in this situation.

2. "dd if=/dev/zero of=/dev/ada5 bs=64k"

3. Drive hits a bad sector which it cannot remap/deal with.  Drive
firmware design flaw results in drive becoming 100% stuck trying to
re-read the sector and work out internal decisions to do remapping or
not.  Drive audibly clicking during this time (not actuator arm being
reset to track 0 noise; some other mechanical issue).  Due to firmware
issue, drive remains in this state indefinitely.

4. FreeBSD CAM reports repeated WRITE_FPDMA_QUEUED (i.e. writes using NCQ)
errors every 30 seconds (kern.cam.ada.default_timeout), for a total of 5
times (kern.cam.da.retry_count+1).

5. FreeBSD spits out similar messages you see; retries exhausted,
cam_periph_alloc error, and devfs claims device removal.

6. Drive is still catatonic of course.  Only way to reset the drive is
to power-cycle it.  Drive removed from hot-swap bay, let sit for 20
seconds, then is reinserted.

7. FreeBSD sees the disk reappear, shows up much like it did during #1,
except...

8. "smartctl -a /dev/ada5" claims no such device or unknown device type
(I forget which).  "ls -l /dev/ada5" shows an entry.  "camcontrol
devlist" shows the disk on the bus, yet I/O does not work.  If I
remember right, re-attempting the dd command returns some error (I
forget which).

9. "camcontrol rescan all" stalls for quite some time when trying to
communicate with entry 5, but eventually does return (I think with some
error).  camcontrol reset all" works without a hitch.  "camcontrol
devlist" during this time shows the same disk on ada5 (which to me means
ATA IDENTIFY, i.e. vendor strings, etc. are reobtained somehow, meaning
I/O works at some level).

10. System otherwise works fine, but the only way to bring back
usability of ada5 is to reboot ("shutdown -r now").

To me, this looks like FreeBSD at some layer within the kernel (or some
driver (I don't know which)) is internally confused about the true state
of things.

Alexander, do you have any ideas?

I can enable CAM debugging (I do use options CAMDEBUG so I can toggle
this with camcontrol) as well as take notes and do a full step-by-step
diagnosis (along with relevant kernel output seen during each phase) if
that would help you.  And I can test patches but not against -CURRENT
(will be a cold day in hell before I run that, sorry).

Let me know, time permitting.  :-)

-- 
| Jeremy Chadwick                                   jdc at koitsu.org |
| UNIX Systems Administrator                http://jdc.koitsu.org/ |
| Mountain View, CA, US                                            |
| Making life hard for others since 1977.             PGP 4BD6C0CB |