disk "flipped" - a known problem?

[Chris Rees]

On 23 February 2013 09:39, Chris Rees <utisoft at gmail.com> wrote:
>
> On 21 Feb 2013 19:07, "Alexander Motin" <mav at freebsd.org> wrote:
>>
>> On 26.01.2013 03:17, Jeremy Chadwick wrote:
>> > Okay, I've figured out the exact, 100% reproducible condition that
>> > causes the situation.  It took me a lot of tries and a digital pocket
>> > recorder to take verbal notes (there are just too many things to look at
>> > simultaneously), but I've figured it out.
>> >
>> > I'm sorry for the verbosity, but it's necessary.
>> >
>> > Assume the disk we're talking about is /dev/ada5.
>> >
>> > 1. Prior to any issues, we have this:
>> >
>> > root at icarus:~ # ls -l /dev/ada5* /dev/xpt* /dev/pass5*
>> > crw-r-----  1 root  operator  0x8c Jan 25 16:41 /dev/ada5
>> > crw-------  1 root  operator  0x75 Jan 25 16:35 /dev/pass5
>> > crw-------  1 root  operator  0x51 Jan 25 16:35 /dev/xpt0
>> >
>> > 2. ada5 begins experiencing issues -- ATA commands (CDBs) submit do not
>> > get a response (not going to discuss how/why that can happen).
>> >
>> > 3. These types of messages are seen on console (naturally the CDB and
>> > request type will vary -- in this case it was because I was doing the dd
>> > zero'ing, thus tickling the bad sector/naughty firmware on the drive):
>> >
>> > Jan 25 16:29:28 icarus kernel: ahcich5: Timeout on slot 0 port 0
>> > Jan 25 16:29:28 icarus kernel: ahcich5: is 00000000 cs 00000000 ss
>> > 00000001 rs 00000001 tfd 40 serr 00000000 cmd 0004c017
>> > Jan 25 16:29:28 icarus kernel: ahcich5: AHCI reset...
>> > Jan 25 16:29:28 icarus kernel: ahcich5: SATA connect time=1000us
>> > status=00000113
>> > Jan 25 16:29:28 icarus kernel: ahcich5: AHCI reset: device found
>> > Jan 25 16:29:28 icarus kernel: (ada5:ahcich5:0:0:0): WRITE_FPDMA_QUEUED.
>> > ACB: 61 80 80 77 01 40 00 00 00 00 00 00
>> > Jan 25 16:29:28 icarus kernel: (ada5:ahcich5:0:0:0): CAM status: Command
>> > timeout
>> > Jan 25 16:29:28 icarus kernel: (ada5:ahcich5:0:0:0): Retrying command
>> >
>> > 4. Any I/O submit to ada5 during this time blocks (this is normal).
>> >
>> > 5. **While this situation is happening**, something using xpt(4)
>> > attempts to submit a CDB to the disk (ex. smartctl -a /dev/ada5).
>> > This request also blocks (again, normal).
>> >
>> > 6. Physical device falls off bus, or CAM kicks the disk off the bus.
>> > Doesn't matter which.  We see messages resembling this (boy am I tired
>> > of this interspersed output problem):
>> >
>> > Jan 25 16:29:32 icarus kernel: (ada5:ahcich5:0:0:0): lost device
>> > Jan 25 16:29:32 icarus kernel: (pass5:ahcich5:0:0:0): lost device
>> > Jan 25 16:29:32 icarus kernel: (ada5:ahcich5:0:0:0): removing device
>> > entry
>> > Jan 25 16:29:32 icarus kernel: (pass5:ahcich5:0:0:0): passdevgonecb:
>> > devfs entry is gone
>> >
>> > 7. Standard I/O requests fail with errno=6 "Device not configured".
>> > xpt(4) requests also fail with the same errno.
>> >
>> > 8. Device-wise, at this stage all we have is:
>> >
>> > root at icarus:~ # ls -l /dev/ada5* /dev/xpt* /dev/pass5*
>> > crw-------  1 root  operator  0x51 Jan 25 16:35 /dev/xpt0
>> >
>> > 9. Device comes back online for whatever reason.  FreeBSD sees the disk,
>> > blah blah blah:
>> >
>> > Jan 25 16:30:16 icarus kernel: GEOM: new disk ada5
>> > Jan 25 16:30:16 icarus kernel: ada5: <WDC WD1500ADFD-00NLR4 21.07QR4>
>> > ATA-7 SATA 1.x device
>> > Jan 25 16:30:16 icarus kernel: ada5: Serial Number WD-WMAP41573589
>> > Jan 25 16:30:16 icarus kernel: ada5: 150.000MB/s transfers (SATA 1.x,
>> > UDMA6, PIO 8192bytes)
>> > Jan 25 16:30:16 icarus kernel: ada5: Command Queueing enabled
>> > Jan 25 16:30:16 icarus kernel: ada5: 143089MB (293046768 512 byte
>> > sectors: 16H 63S/T 16383C)
>> > Jan 25 16:30:16 icarus kernel: ada5: Previously was known as ad14
>> >
>> > ...um, where's pass5?
>> >
>> > 10. /dev/pass5 is now completely (permanently) missing:
>> >
>> > root at icarus:~ # ls -l /dev/ada5* /dev/xpt* /dev/pass5*
>> > crw-r-----  1 root  operator  0x99 Jan 25 16:42 /dev/ada5
>> > crw-------  1 root  operator  0x51 Jan 25 16:35 /dev/xpt0
>> >
>> > 11. Any further attempts to communicate via xpt(4) with ada5 fail.
>> > Detaching and reattaching the disk does not fix the issue; the only fix
>> > is to reboot the system.
>> >
>> > 12. "camcontrol debug -IPXp scbus5" results in tons and tons of output
>> > all pertaining to xpt(4).  It looks like xpt(4) is in some kind of
>> > loop.
>> >
>> > Below is my verbose boot (with non-kernel things removed), which
>> > also includes "camcontrol debug" output once things are in a bad state:
>> >
>> > http://jdc.koitsu.org/freebsd/xpt_oddity.log
>> >
>> > In this log you'll see that after 1 CAM timeout I yanked the drive, then
>> > roughly 30 seconds later reinserted it.
>> >
>> > If you need me to turn on CAM debugging *prior* to the above, I can do
>> > that, just let me know.
>> >
>> > The important step is #5.  Without that, the problem shown in #9/10/11
>> > does not happen.
>> >
>> > It's a good thing I don't run smartd(8) -- most users I see using that
>> > software set the interval to something like 180s or 60s.  Imagine this
>> > frustration: "okay so the disk fell off the bus, but what, now I can't
>> > talk to it with SMART?  Uhhh... <reboots>  Err, works now?  Whatever".
>>
>> I think, the problem may already be fixed in HEAD by r244014 by ken at .
>> I've just merged it to 9-STABLE at r247115. So if it is still possible
>> to reproduce the situation, it would be good to try.
>
> I think I've been having the same troubles since upgrading from 9.0, so I'm
> going to try applying that to 9.1-R and I'll also give feedback.

Yup, I no longer get weird disconnects after this patch (5 days later now).

Thank you very much!

Chris