[comp.sys.sgi] ExaByte feom problem

FL17@DLRVMBS.BITNET (03/20/91)

To: 			info-iris@brl.mil			19-Mar-1991

ExaByte feom problem

Hi,

the sequence

	mt -t /dev/nrexa rewind
	mt -t /dev/nrexa feom
	bru -cvf /dev/nrexa files ...

works nicely on our 4D70GT running IRIX 3.3.1 to create multiple archives
on an ExaByte tape as long as the machine is not rebooted. If, however,
the machine is rebooted, feom doesn't work as expected and a new archive is
written at the beginning of the tape overwriting what was already on tape.
If the machine is not rebooted again, the next archive is appended to the
archive already on tape.

Does anyone out there have any explanation or workaround ?

Thanks and best regards

Ralf Beyer

---------------------------------------------------------------------
Ralf Beyer	| German Aerospace Research Establishment
		| Braunschweig Research Center
		| Institute for Flight Guidance
		| Flughafen
		| D-3300 Braunschweig, Fed. Rep. of Germany
		| Phone: (0531) 395-2530
		| Fax:	 (0531) 395-2550
		| Email:         fl17@dlrvmbs.bitnet
		| Email (local): beyer@bflsgu
---------------------------------------------------------------------

FL17@DLRVMBS.BITNET (03/21/91)

To: 			info-iris@brl.mil			19-Mar-1991

ExaByte feom problem

Hi,

the sequence

	mt -t guest@remhost:/dev/nrexa rewind
	mt -t guest@remhost:/dev/nrexa feom
	bru -cvf guest@remhost:/dev/nrexa files ...

works nicely on our 4D25GT with the remote host being a 4D70GT to create
multiple archives on an ExaByte tape as long as the remote host is not
rebooted. If, however, the remote host is rebooted, feom doesn't work as
expected and a new archive is written at the beginning of the tape overwriting
what was already there. If the remote host is not rebooted again, the next
archive is appended to the archives already on tape as expected.

If the same procedure is run on a local host, i.e.

	mt -t /dev/nrexa rewind
	mt -t /dev/nrexa feom
	bru -cvf /dev/nrexa files ...

this error does not show up.

Does anyone out there have any explanation or workaround ?

Both machines are running IRIX 3.3.1.

Thanks and best regards

Ralf Beyer

---------------------------------------------------------------------
Ralf Beyer	| German Aerospace Research Establishment
		| Braunschweig Research Center
		| Institute for Flight Guidance
		| Flughafen
		| D-3300 Braunschweig, Fed. Rep. of Germany
		| Phone: (0531) 395-2530
		| Fax:	 (0531) 395-2550
		| Email:         fl17@dlrvmbs.bitnet
		| Email (local): beyer@bflsgu
---------------------------------------------------------------------

olson@anchor.esd.sgi.com (Dave Olson) (03/21/91)

In <9103200941.aa07171@VGR.BRL.MIL> FL17@DLRVMBS.BITNET writes:

| the sequence
| 
| 	mt -t guest@remhost:/dev/nrexa rewind
| 	mt -t guest@remhost:/dev/nrexa feom
| 	bru -cvf guest@remhost:/dev/nrexa files ...
| 
| works nicely on our 4D25GT with the remote host being a 4D70GT to create
| multiple archives on an ExaByte tape as long as the remote host is not
| rebooted. If, however, the remote host is rebooted, feom doesn't work as
| expected and a new archive is written at the beginning of the tape overwriting
| what was already there. If the remote host is not rebooted again, the next
| archive is appended to the archives already on tape as expected.

The bug is in the setup of the drive on the very first use after
reboot (or after a tape is first inserted, if I remember correctly).

The hack work-around till 4.0 is to add after the rewind:

	mt ... fsr 1

and ignore any resulting errors (which might occur if the tape
is blank).

Sorry about that; it only happens on the Exabyte, due to the fact
that it doesn't support space to EOD, and it therefore has to be
faked; some condition codes weren't set/checked correctly in this
one case.
--

	Dave Olson

Life would be so much easier if we could just look at the source code.