Sue -- You have a number of areas to study.  You should get an 
understanding of the capabilities of your system (tape drive, cpu, 
network and clients presenting data to the network) in terms of (1) what 
is theoretically possible and (2) what you are seeing during the backups. 

Learning about these two areas will allow you measure how you are doing 
with respect to a theoretical maximum.  You probably won't reach the 
maximums, but you'll have a better understanding of your system and 
perhaps get ideas of where to focus.

Your actions should include "tuning".  Veritas has TechNotes on their 
support web site to help.  In general, getting the most from your tapes 
will mean maximum buffer size for the tapes and near maximum number of 
buffers.  This allows for maximum performance of your tapes.  The tapes 
can still be held back by the network, so this area should be looked 
at.  Just a couple of clients with poor network settings, slow links or 
being unreachable can wreak havoc with backup schedules, especially when 
you have just once source stream for each tape.

Which brings us to multiplexing (MPX).  Multiplexing is your best friend 
when your client systems can't get data to your backup system fast 
enough to keep your tapes spinning.  They will impact restore times 
(little impact for slow clients, perhaps significant impact to fast 
clients), but they give you your best chance to complete backups in 
minimum time.

With all that done, if you have a client with multiple independent data 
sources that isn't using all of its network connection, multiple data 
streams may help. (A lot of "if"s!).  Multiple data streams is enabled 
in a policy and controlled at the client level with a master server 
"client  attribute", possibly with the help of specifying "new stream"s 
in the backup selection list of a client's policy.

With that done, you're into adjusting backup schedules, expectations 
and/or hardware/methods.

Hope this helps!     cheers, wayne

Preece, Sue wrote, in part,  on 1/13/2005 5:02 AM:

>I'm currently running Netbackup Business Server ver 4.5 and have 2 tape
>drives available for backups.
>
>I have a policy which is configured to backup 2 drives on server, an
>approx total of 140gb, which is taking far to long to backup and is now
>stopping me carrying out duplicates.
>
>Would allowing multiple data streams help and if so how do i configure
>it.
>