Not much I can add to the replies already received. I agree with Barton that
parallelism is usually the lowest hanging fruit. You could also look at:

 * Network setup and configuration. Sometimes there are performance issues
in networks where auto negotiation and auto sensing are not being handled
correctly. Bigasm will of course help you find what the best performance
under existing cfg can be. But, if you can, the simplest way to see what's
going on is to start running tests with duplexing and auto
sensing/negotiation turned off. If there is a significant performance
increase, then you have some trouble shooting to do on your network. You
probably already know this stuff like the back of your hand, but just in
case, there's a very nicely written overview of what is at play here that
can be found at: http://www.cites.uiuc.edu/network/advanced/autosense.html

 * Tape block size. Haven't seen a great need for tuning with LTO2. But
perhaps someone else's experience may be different.

 * File system handling. There are times when parallelism of file walkers
(the classic NetWorker - or NetBackup or CommVault or anyone else for that
matter - mechanism to send data to a storage node) simply is not enough to
get the job done. This is the case when you have what is sometimes called a
"high density file system", or one where there are many small files. One of
the classic symptoms of a high density file system is a file backup of about
2 to 4MB/s in unix (I'm afraid it is even slower in Windows). Your best
alternative when you run into an hdfs is to bypass file walking and backup
the image or file system as a whole.

This is all that comes to mind at the moment. 

I hope it is of some use to you.

To sign off this list, send email to listserv AT listserv.temple DOT edu and 
type "signoff networker" in the body of the email. Please write to 
networker-request AT listserv.temple DOT edu if you have any problems with this 
list. You can access the archives at 
http://listserv.temple.edu/archives/networker.html or
via RSS at http://listserv.temple.edu/cgi-bin/wa?RSS&L=NETWORKER