Hello List

this has been discussed already some times on the list but as i have  
ssen no real conclusion i will ask for opinion again. The setup is  
Bacula 5.2.10 on Ubuntu 12.04 LTS (x64) with a LTO-4 drive connected  
through Adaptec 29320LPE, a 320MByte/sec PCI-Express controller. To  
prevent the LTO-4 tape from shining/whining around we use the Data  
spool feature on a SSD drive (Intel Postville Refresh 120GB) with  
"Maximum Spool Size = 20GB" and "Maximum File Size = 4GB". This works  
as expected beside the fact that the transfer spped max. out at  
~84MBytes/sec with encrypted data (hard to further compress) and  
86MBytes/sec without encryption when using Bacula. To test if the  
hardware is to blame i have done some simple dd to tape like this

"dd if=/some/file of=/dev/nst0 bs=xxK"

which lead to ~110MBytes/sec with bs=64K and ~140MBytes/sec with bs=1M

As the tape is altering speed all the time with Bacula i would like to  
know if there is a possibility to get closer to the dd values and what  
could be the bottleneck in such a setup?
It would also be helpful if someone has compareable results for LTO-4  
with Bacula to see if we are on the right track.

Many Thanks

Andreas




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