Reading the mail archive, it seems I'm not alone in wanting to see concurrent 
spooling/despooling.

Could we hand off the job to a standalone spooler like mbuffer 
(http://www.maier-komor.de/mbuffer.html)? For a simple tar to LTO-4 job it 
makes a tremendous improvement.

The Bacuala developers would need to modify the storage daemon to allow the 
datastream to be diverted out and then back in through a pair of FIFOs before 
it gets [properly re-blocked? and] written to tape. The user would need to tie 
the FIFOs together with an external spooler. It might look like this:

------/etc/bacula-sd.conf------
<snip>
Device {
  ...
  PushToFIFOSpooler = /path/to/bufreceive        # bufreceive is a FIFO on this 
machine
 PullFromFIFOSpooler  = /path/to/bufsend         # bufsend is also a FIFO
  ...
}
</snip>

------/etc/bacula-dir.conf------
<snip>
Job {
  ...
  RunBeforeJob = "mbuffer -i /path/to/bufreceive -o /path/to/bufsend" # default 
puny 2M RAM buffer; can be set to multi-gig RAM or disk
  # Alternatively: RunBeforeJob = "mbuffer < /path/to/bufreceive > 
/path/to/bufsend"
  ...
}
</snip>

This would

-          be a lot easier than asking the developers to reinvent the wheel 
(insert your own ring-buffer pun here...)

-          let the developers all but ignore spooling & focus on real backup 
stuff

-          give users access to many more options, such as using RAM or disk 
spool, high/low-watermarks, and rate-limiting

-          let folks cleverer than me figure out other cool things to do with 
the datastream

Thanks,
Dan Stieneke
IT Specialist
USDA - ARS - NWISRL
3793 N 3600 E
Kimberly, ID 83341
208/423-6519





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