Ok, maybe I'm missing something.

One recommendation regarding streaming is not to have multiple streams 
off the same physical device.  By physical device, I am also taking that 
to mean a RAID device that spans multiple disks and/or disk arrays.  In 
my case I have four arrays partitioned into 11 LUNs each and then my 
filesystem is built on a volume striped across all 44 LUNs.

So, I have a 400 GB (for now, but growing) data set on that filesystem. 
  My library's 8 AIT-3 tape drives can write at up to 40 GB/h each. 
Therefore if I were to have a single stream the data set would take 10 
hours to back up.  But if I want it to complete in, say, 2 hours, I'd 
have to use 4 drives and hence define 4 roughly equal size streams 
(which is what I currently do), which I occasionally have to rebalance 
as the data set grows.  But this streaming goes against the above 
recommendation.

It's possible this really isn't a problem if it just boils down to the 
drawback of the streaming taking more time due to additional head 
movement.  Breaking up a huge stream more than compensates for that 
overhead.

Any comments or suggestions?

Justin

-- 
Justin C. Lloyd
Unix System Administrator
MCI System Technology Solutions
Office 703.886.3219 Vnet 806.3219