Hans-Ole Kaae writes:

>(I'm thinking on how much you can expect to hold on one tape - using both
>the built-in hardware compression
>plus ORBiTs software ditto).

Using both hardware and software compression will result in a decrease in
performance, capacity or both. The reason is that compression works by
removing redundant information from a data stream. Once ORBiT's code has
removed the redundancy, there's nothing left for the tape drive to do,
and you incur the overhead of the compression logic and formatting
without further reducing the amount of data on the tape.

In general, I use software compression in preference to hardware
compression, though most people recommend the opposite. The advantage to
software compression is that it can take the type of data into account.
My Unix backup utility, for example, knows about compressed and gzip'd
files and does not try to compress them. On the other hand, software
compression is practical only when the computer is not doing anything
else during the backup, since the compression is CPU-intensive. Since my
backups run at night with nobody else on the system, that's not an issue
for me.

-- Bruce


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