Our backup system is two media servers with two gigabit NIC's in each 
one.  The mix of systems in our environment has left us with some hosts 
on 100Mbps only, and some with the ability to have two cards, the other 
one being gig.  We created a subnet for the gig interface, and for those 
hosts that can support two interfaces, I back them up by calling them by 
their gigabit interface DNS name.  99% of the backup traffic then goes 
over this port.  I can get three tape drives on each server running at 
full speed, but can't seem to get four.  

Sun trunking works in theory, but has not proven to be 2Gbps of total 
throughput.  My experience has shown me that a trunked interface on a 
system means it is possible for two hosts to achieve full gigabit speeds 
to and from this server, but not for one host to achieve the bandwidth 
of both interfaces.  Our foundry switch does not support the round 
robin, and I'm told this is the protocol necessary to get up to the 
2Gbps limit.  In my opinion, it's not worth the $900 plus yearly support 
fees.

The suggestion for adding another media server is a good way to balance 
the load.  SSO is another good alternative.  It costs more.

If 10 Gbps ethernet ever becomes available, then most of this problem 
will disappear.  Then we'll have bottlenecks elsewhere.

-Jon