Efficient tape I/O with 386/ix; How??

[Wietse Z. Venema]

In article <317 at focsys.UUCP> larry at focsys.UUCP (Larry Williamson) writes:
>Streaming tape I/O with 386/ix seems to be rather slow.  The drive
>is not streaming very well.  It spends most of it's time stopping
>and starting.  I'm using an Everex Excel 60 with a long controller
>card. 

You may consider using the ddd command that was posted earlier this year
in one of the source groups by Tapani Lindgren <nispa at cs.hut.fi>. The
following is an excerpt from the man page:

          Ddd works almost the same way as dd(1), but it has a much
          better throughput, especially when used with slow i/o-
          devices, such as tape drives.  The improvement is achieved
          mainly by dividing the copying process into two processes,
          one of which reads while the other one writes and vice
          versa.  Also all code conversion capabilities are omitted.
          There is no additional overhead copying data between various
          conversion buffers.

          Ddd was inspired by the vast difference in speed between
          BSD4.2 and BSD4.3 dumps - in BSD4.3 dump(8) writes to raw
          magnetic tape with several processes, thus keeping the tape
          continuously in motion.  I wanted to get the same
          improvement to remote dumps, so this filter was needed.
          Adding it to any pipeline of commands usually increases the
          throughput (that is, if you have enough MIPS).
-- 
work:	wswietse at eutrc3.uucp	| Eindhoven University of Technology
work:	wswietse at heitue5.bitnet	| Mathematics and Computing Science
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