Subject: Trying to read from a FITS format exabyte tape

From: marcos at embezzle.stanford.edu (Marcos J.J. Montes)
Date: Wed, 10 Nov 93 17:57:00 GMT

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Hello-
	I was wondering if anyone out there would be able to help.
We have a problem here. There are tapes of observations that in the past have 
been successfully read with the command 
 	dd if=/dev/nrmt0h of=x ibs=28800 obs=2880
However, we have rearranged the system for various reasons, and the exabyte drive
is attatched to a VAXStation3100 running Ultrix 4.3 . Apparently the version
of dd under this Ultrix on VAXStations cannot handle ibs>16k . Does anyone 
have some suggestions for a way to read the tape in its current setup and
be able to read all the blocks? We would hate moving the tape drive to another 
machine (for access reasons) but it is a possibility.

Is fits always written with ibs=28800? Any help would be appreciated.

Marcos

***********Please replay to marcos at embezzle.stanford.edu******************
-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Treat the earth well;                   |Marcos Montes        
it was not given to us by our parents:  |qozer at leland.stanford.edu
it was loaned to us by our children.    |marcos at mensch.stanford.edu
-Kenyan proverb                         |marcos at embezzle.stanford.edu
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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From: tody at lepus.tuc.noao.edu (Doug Tody)
Date: Wed, 10 Nov 1993 20:42:08 GMT

> Is fits always written with ibs=28800? Any help would be appreciated.

Marcos,

The problem is not with DD, but with the SCSI tape interface on VAX/Ultrix
systems.  This system is unusual in that it has a maximum record length of
16K bytes.

There may be some trick you can use to read the tape, but I doubt it.  The
device driver will want to return an error if the read request does not read
a full tape record, but you can't read a full record without exceeding the
max transfer size, so probably you are stuck.  Probably you will need to
move the drive to another host.

	Doug Tody