[Dump-users] Performance

[David G. <dj...@dr...>]

   I am running Redhat 6.1 with dump 0.4b18-1.  On some disks dump gives
much poorer performance that tar.  I can improve it some using hdparm to
change the number of blocks read ahead.  Is their any better way to
improve the performance?  The example here is a old machine with slow disk.
The newer machine has the same performance issue on a 1.6G that came with
it.  The 20G I added later doesn't show this problem.

Commands used for testing
time tar --atime-preserve -c -l -b 64 -f - -C /mnt/pdp . | cat > /dev/null
time dump 0bBfu 32 20971520 /dev/null /mnt/pdp

For read ahead 8 (hdparm raw disk speed .91 MB/sec)

tar
3.09user 172.07system 5:41.55elapsed 51%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (76506major+98minor)pagefaults 0swaps

dump (50% the speed of tar)
  DUMP: finished in 661 seconds, throughput 448 KBytes/sec
16.53user 194.68system 11:22.68elapsed 30%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (193major+200minor)pagefaults 0swaps

For read ahead 64 (hdparm raw disk speed 1.42 MB/sec)

tar
3.54user 165.21system 5:35.14elapsed 50%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (76540major+98minor)pagefaults 0swaps

dump (85% the speed of tar)
  DUMP: finished in 378 seconds, throughput 784 KBytes/sec
17.29user 207.91system 6:32.97elapsed 57%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (185major+201minor)pagefaults 0swaps

Thanks,
David Gesswein
http://www.pdp8.net/  -- Old computers with blinkenlights