Re: [Dump-users] Dump 10 times slower on faster system

[Bob B. Jr. <bl...@da...>]

Well it seems to be all in the block size.  On both systems I was using
1024k block size, which we find is optimal for writing to tape.  dump
doesn't like this.  I started experimenting with different block sizes.

I found the sweet spot at 64k blocks.

Using 64k block size yields the fastest dump to tape throughput at about
50 MB/s  (still slower than older dump, but only marginally).

root@appserver-wn:~# dump 0uf /dev/st0 -b 64 /opt
  DUMP: Date of this level 0 dump: Thu Jan 12 15:57:58 2012
  DUMP: Dumping /dev/mapper/vg1-opt (/opt) to /dev/st0
  DUMP: Label: none
  DUMP: Writing 64 Kilobyte records
  DUMP: mapping (Pass I) [regular files]
  DUMP: mapping (Pass II) [directories]
  DUMP: estimated 4999550 blocks.
  DUMP: Volume 1 started with block 1 at: Thu Jan 12 15:57:59 2012
  DUMP: dumping (Pass III) [directories]
  DUMP: dumping (Pass IV) [regular files]
  DUMP: Closing /dev/st0
  DUMP: Volume 1 completed at: Thu Jan 12 16:00:06 2012
  DUMP: Volume 1 4990336 blocks (4873.38MB)
  DUMP: Volume 1 took 0:02:07
  DUMP: Volume 1 transfer rate: 39293 kB/s
  DUMP: 4990336 blocks (4873.38MB) on 1 volume(s)
  DUMP: finished in 96 seconds, throughput 51982 kBytes/sec
  DUMP: Date of this level 0 dump: Thu Jan 12 15:57:58 2012
  DUMP: Date this dump completed:  Thu Jan 12 16:00:06 2012
  DUMP: Average transfer rate: 39293 kB/s
  DUMP: DUMP IS DONE