On Mon, 15 Sep 1997, Richard B. Johnson wrote:
>
> To the maintainer of the SCSI Tape Driver, greetings!
> I have noticed a problem starting with kernels this early Spring. If
> there are any SCSI Tape errors, the errors seem to persist until the
> machine is rebooted.
>
> For instance:
>
> # cp /dev/zero /dev/st0
> cp: /dev/st0: I/O error
> cp: /dev/st0: I/O error ! This fails after a few minutes.
> # mt status
> SCSI 2 tape drive: ! This doesn't show any errors
> File number=0, block number=0, partition=0.
> Tape block size 512 bytes. Density code 0x45 (unknown).
^^^^
What drive does this density belong to?
> Soft error count since last status=0
> General status bits on (41010000):
> BOT ONLINE IM_REP_EN
> # ! Cleaned drive, inserted brand-new tape.
> # cp /dev/zero /dev/st0 ! Instantly fails without even attempting to
> cp: /dev/st0: I/O error ! access the physical device.
> cp: /dev/st0: I/O error
I have tried to recreate this problem in my system. I don't have a broken
tape but I modified the mid-level scsi_done function to turn EOM into
Medium Error. In my system (Adaptec AHA2940, HP C1533) the errors don't
persist. After re-inserting the tape, I can rewrite it without problems.
...
> It appears as though the driver "remembers" that there was a previous
> command-completion failure and refuses to attempt the command again.
> Actually, it's not the driver that remembers, it's the controller. The
^^^^^^^^^^^^^^
or the drive
> driver seems to get sense data before each command rather than after,
> and refuses to execute the new command because of bad sense data. This bad
> sense data was from a previous command.
>
> Sep 15 10:10:32 chaos kernel: st0: Error with sense data:
> Current error st09:00: sns = f0 3
...
> Sep 15 10:10:32 chaos kernel: st0: Error with sense data:
> Current error st09:00: sns = f0 3
...
Getting twe same medium error twice is what I expect to happen if the
drive finds a medium error: the driver tries to write the closing filemark
after the error and this probably also fails.
Kai