Hi everyone,

Our setup consists of a Dell 2950 server (PERC6i) w/ FreeBSD7 and two HP
Ultrium LTO4 drives installed in a twin Quantum autochanger enclosure. 
Our bacula version is 5.0.0 (which is the current FreeBSD port version). 

Here is our problem:

When running a single job, our setup is able to consistently surpass
70Mbytes/sec (or even 80) on despooling, which should be reasonably
enough.  Unfortunately, when running several jobs on both drives (for
example 6+6 parallel jobs) our despooling speeds drop to about
20Mbytes/sec or even less. The speed of the jobs to finish last
naturally ramp up, especially for the very last. Our hypothesis is that
the spooling area cannot handle simultaneous reading (from jobs that are
still tranfering) and writing (from the currently despooling job) too
well, hence the performance loss. 

So far we were using a common spool area for both drives on these two
test setups:

1)A spool area on a Clarion CX4 Fibre Channel array (4Gbps) w/ 2x10Krpm
disks on a raid0 configuration. 
2)A 2xSCSI320 raid0 striped configuration in the server itself (via the
PERC6i controller).

Both setups yielded similarly poor results.

Our thoughts/questions:

-Should we use a separate spool area for each drive? 
-Anyone else that has had problems with the despooling speed being too
low? What are your proposed solutions, if any?

I realize this is not strictly a bacula question, however the matter
should be of interest for any bacula admin out there. I understand that
under like 40Mbytes/sec the drive constantly starts and stops, a
process which  is detrimental to its expected lifetime (and the tape's
as well). 


Best Regards,
-- 
Athanasios Douitsis, 
National Technical University of Athens NOC

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