On Tuesday 10 June 2003 09:16, Tom Yates wrote:
>On Mon, 9 Jun 2003, Eric Siegerman wrote:
>> Well, "SCSI parity error" seems pretty clear -- data being
>> received with bad parity by one of your SCSI devices (either the
>> tape drive or the SCSI adapter; I'm being carefully agnostic as
>> to which way the data's flowing when the errors are detected).
>> Most likely the corruption is occurring on the SCSI bus.  The
>> only other possibility I can think of is a firmware bug or other
>> malfunction in one of the two devices.
>
>seems reasonable.
>
>> > can you think of any other non-amanda test i can do that will
>> > exercise the tape drive as amanda does?
>>
>> Only what I've already suggested -- use real disk files instead
>> of /dev/urandom as your data source.  Based on what I'm about to
>> say, it'd be wise to make sure those files come from the same
>> drive your Amanda holding disk is on.  To get as close as
>> possible to what Amanda's doing, use the holding-disk files
>> themselves.
>
>ok, i did this (made a big disc file from /dev/urandom, then dd'ed
> that to the tape), and it still works fine.  i emphasise that my
> discs aren't on the same SCSI bus as the tape drive - the tape
> drive has its own controller, which no other device uses - but
> still no errors came.  i dd'ed around 2GB of data to the tape, and
> had no problems at all.
>
>> If, as I suspect, the problem is noise on the SCSI bus, one ugly
>> possibility is that your SCSI cable is picking up noise from the
>> rest of the system; for example, from the IDE cable that your
>> disk is connected to.  No disk I/O => no noise being transmitted
>> => no SCSI errors.
>
>hopefully, this test has disproved that theory.
>
>> The obvious first stab at an answer would be to just move the
>> cables around inside the case, hoping to get the SCSI cable far
>> enough away from the noise source.  But *please* figure out how
>> to duplicate the problem first, otherwise you'll never know if
>> you fixed it!
>
>at the moment, duplicating it is *really* easy.  any time the amanda
> taper tries to write to the tape, nothing works (write errors in
> the first gigabyte).  the rest of the time, i can send data to the
> tape just fine.
>
>> A better solution (if this is indeed the problem!) would be
>> better-quality SCSI cables.
>
>so noted.
>
>> This is the sort of problem I *hate*!  Best of luck with it.
>
><grin> thanks for your ideas!  does anyone else have any
> suggestions, at all, for a tape drive which seems to be fine until
> amanda uses it, and which then goes south fairly rapidly?
>
Blocksize clashes with a tape drive that doesn't use a variable block 
size maybe?  I'm just learning about that myself.  Post an "mt -f 
/dev/device status" please.

>does anyone know anything about decoding kernel SCSI error messages?

Not here, but you might post a few lines of it, it might ring someones 
bell :)

-- 
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz  512M
99.26% setiathome rank, not too shabby for a WV hillbilly
Yahoo.com attornies please note, additions to this message
by Gene Heskett are:
Copyright 2003 by Maurice Eugene Heskett, all rights reserved.