RS/6000 Tape questions

[Duty Programmer]

In article <496 at nwnexus.WA.COM> wjones at nwnexus.WA.COM (Warren Jones) writes:
>rmilner at zia.aoc.nrao.edu (Ruth Milner) writes:
>
>>We have found the Exabyte tape handling (don't have any other kind) to be ...
>>unusual ... compared to the Suns. For example, on a Sun, if you write a file
>>onto Exabyte, you can take it away and later on put it back in, skip to the
>>end of that file, and write another one. On the RS/6000, not only will it not
>>do this at all (I/O error), but if you take a tape with a file written on it 
>>by the IBM over to the Sun, the Sun won't write at the end of it any more 
>>either! Clearly it's writing something different, but we haven't been able
>>to find out what. Anybody have any clues? According to the documentation, 
>>they both write a double eof on close, and that doesn't really cause us any
>>serious problems.
>

I sympathise. The AIX tape i/o has been driving me crazy for several weeks.

However, I think this last problem you mention may be something else. You don't
mention whether you can read the IBM tapes on the Sun. If you can't, then it
may be that the Sun is using CRC error correction and the IBM is using ECC.
You can get the IBM to use CRC by either changing the characteristics of the
tape driver (via chdev), or by piping tape writes through 'tctl t write'.
Check InfoExplorer for more information.

We have had no trouble with 8mm tapes, but the QIC tapes are driving us crazy.
Both 'tar' and 'dd' seem to be broken with respect to tape i/o, although it
seems that 'tctl' can always read and write tapes. The diagnostic is always
'bad argument', which is rather unhelpful. We have changed the block size from
512 to 0 (variable), and the damn thing still doesn't work.

In case IBM is listening, we are running release 3.01.0004.0017 bos.obj.


rab
---
Richard Brown                     | E-mail: rab at tauon.ph.unimelb.edu.au
School of Physics                 | Phone : +61 3 344 5081
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