Re: Interesting speed benchmarks

Robert Huff wrote:
 >         As long as we're on the subject:
 >         I'm testing a USB-connected external hard drive (PATA-133) as a
 > replacement for SCSI-I/DLT in a dump-driven backup arrangement for a
 > P4/2.25 ghz+80 mbyte/sec SCSI box.
 > [...]
 >         Performance, so far, has been better than the old set-up but far
 > less than thrilling and I'd like to understand why.  Dump, using
 > these options: 
 > 
 >         $DUMP_LEVEL -D $DUMPDATES_FILE -Lau -f 
 > 
 >         gets me 2 +/- 0.2 mbytes/sec.
 >         Is this a reasonable value?  (I.e. is dump the limiting
 > factor?)  Do I need to reconfigure something, or is my hardware just
 > lame?
 >         I'm not expecting to get the full 40 mbyte/sec of USB 2.0 spec;
 > 20 or even 10 would be fine.  But 2?  Ouch.

Historically the performance of dump(8) has always been
quite bad.  It didn't matter in ancient times because
tape drives were slow back then, so dump(8) was not the
limiting factor.  ;-)

For that reason I try to avoid dump(8) when possible.
Maybe you should try to use tar, cpio or pax instead and
check if the performance is better.

I'm not sure if dump(8) has been improved recently (I
confess that I haven't tried).  Maybe it is better now.
If you continue to use dump(8), make sure that you
specify a reasonable cache size (-C option).  Refer to
the manual page for details.  Without that option,
performance will be _really_ bad.

Best regards
   Oliver

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