[Bacula-users] IBM TS-3100 too slow on bacula

Hello,

My Hardware:
   Blade Center H, with 8 blades LS21 (1 AMD Opteron 2.4GHz, 6 GB ram)
   The data comes from a SAN DS4700 (Fiber channel 4 Gb/s).
   My tape library is a IBM TS3100 using tapes LTO-3 connected via fiber
   channel.

My Software:
  OS: Red Hat Enterprise Linux ES release 4.
  I'm using bacula-2.4.3


I've started with bacula 2.2.8 six months ago, making backups on disk. Then
I made some test with the tape backup, following "Testing Your Tape Drive
With Bacula", getting excellent BW. But then I upgraded to bacula 2.4.3 and
somehow I ended misconfiguring my tape unit.

Now, backing up 15MB from the SAN to the tape takes almost 8min. My tape
BW is just 33.0 KB/s. I tried backing up local data with the same BW.
Then, I'd go back to the basic tests and discovered that the tape unit is
working slow even without bacula. Example:

  # time dd if=/dev/sda of=/dev/IBMtape0 bs=1M count=100

takes 3min (572 KB/s). Changing bs=64K doesn't make too much difference.
I get equivalent BW using tar. So, it seems to be a tape unit problem,
but then I ran the IBM test program 'itdt' and got these numbers:


   Block Size  Data Size    Elapsed    Data Rate
      (KB)       (MB)       Time (s)    (MB/s)
  +-----------+-----------+-----------+-----------+
  | 512       | 41961     | 245.728   | 170.764   |
  | 256       | 41961     | 242.377   | 173.125   |
  | 128       | 41961     | 259.317   | 161.815   |
  | 64        | 41961     | 293.884   | 142.783   |
  | 32        | 41961     | 354.081   | 118.508   |
  | 16        | 41961     | 484.687   | 86.5746   |
  | 8         | 41961     | 746.556   | 56.2069   |
  +-----------+-----------+-----------+-----------+


So, the tape unit seems to be OK, after all.

My question is: is there a parameter in bacuala that allow me improve the
BW of my tape unit?

My actual configuration looks like this:

bacula-sd.conf:
==============
  [...]

  Device {
    Name = TS3100
    Archive Device = /dev/IBMtape0
    Device Type = Tape
    Media Type = TS3100
    AutoChanger = yes
    AlwaysOpen = yes
    Removable Media = yes
    Random Access = no
    Requires Mount = no
    Hardware End of Medium = no
    Fast Forward Space File = no
    BSF at EOM = yes
    Two EOF = yes
    #Offline on Unmount = yes
    Drive Index = 0
    Maximum Spool Size = 200100100100
    Maximum Job Spool Size = 200100100100
    Spool Directory = /reduc/var/bak/general/spool
  }

Any ideas?

Thanks in advance.


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