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From: karish@pangea.Stanford.EDU (Chuck Karish)
Subject: Re: SCO Can't Read 8-mm Tape Written by Ultrix.
Message-ID: <1992Sep19.193954.1497@morrow.stanford.edu>
Summary: block size conflict?
Sender: news@morrow.stanford.edu (News Service)
Organization: Mindcraft, Inc.
References: <BusMMF.12I@npt1.uucp>
Date: Sat, 19 Sep 1992 19:39:54 GMT
Lines: 42
In article <BusMMF.12I@npt1.uucp> root@npt1.uucp writes:
> I need to transfer data via 8-mm tape (Exebyte 8800 drives on both
>systems) from an Ultrix 4.2A system to a SCO 3.4 system. So far, I have been
>unable to do so.
> From what I've been able to find out so far, Ultrix seems to use a fixed
>block size of 512 bytes and SCO a fixed block size of 10,240, but I'm not
>sure about either piece of information.
>
> For my next attempt, I'm going to try archiving to a file and then using
>dd to transfer to and from the tape [ ... ]
This won't work.
> Has anyone out there ever managed to transfer data from Ultrix to SCO on
>8-mm tape? I would also greatly appreciate any ideas as to what I might try
>next or any insights as to what the problem is.
I tried reading tapes written on Suns and RS/6000s on an
SCO system, with no success. The SCO system tells me
"block size 0", saws thew tape back and forth, and gives up
after three or four minutes.
As I recall, the other systems could read tapes written on
the SCO system. When I moved the drive to the Sun, it
could read AIX tapes with no problems.
My guess is that the Exabyte tape format includes a header
at BOT that tells the driver what blocking factor is used.
On AIX, a factor of 0 means "variable block size:, meaning
that the utility that accesses the tape is responsible for
reading data in the correct block size.
By the way, the native block size on Exabyte drives is 1024
bytes, so if ULTRIX is writing 512-byte blocks it's wasting
half the capacity of the tape and writing more slowly than
it could. If you can, write in block sizes that are multiples
of 1K.
--
Chuck Karish karish@mindcraft.com
(415) 323-9000 x117 karish@forel.stanford.edu