[Bacula-users] bacula performance with spooling when writing to tape from fd

[Joe D. <jo...@li...>]

I've run into a performance problem when doing backups to tape that I 
need some help in resolving.  According to the output from btape test, 
my tape drive can be written to at around 9,700 KB/s.  I've also run a 
test with the Windows file daemon and can backup to disk on my bacula 
server at around 9,000 KB/s.  Based upon these two figures, I would 
assume that I should be able to do a backup from the Windows file daemon 
to tape at 9,000 KB/s - which over my 100 megabit network I'd be very 
happy with.  However with spooling disabled my backup to tape runs at 
about 6700 KB/s (using the same job which gave me 9000 KB/s before).  
With spooling enabled my backup runs at approx 4700 KB/s.

One of my servers has about 240GB of data that I need to run a full 
backup on weekly, however my bacula server only has about 100GB of 
available disk space.  As I don't have enough disk space to spool the 
entire job to disk first, the FD is going to be sitting idle while the 
SD writes the first 100GB to disk, and then the process will be repeated 
again, and again for the final 40GB.  Is there anything I can do in 
bacula to allow the FD to keep spooling data to the SD while the SD is 
writing data to tape?  Are there any other workaround I could use, or am 
I going to have to buy a bigger hard drive for my backup server?

Thanks,
Joe