Veritas Backups and Unix Agent

i've got three unix servers that are all running redhat 9 and enterprise3 (2 are the later) with unix agents.  I've got a windows 2000 server running veritas 9.1 and backing up something to the tune of about 25 other servers (beyond the 3 unix boxes) and for those 25 servers, its pretty much 100-400 megs a minute on backups, but for these unix servers, it averages about 40-50 megs a minute.  The backups do run and they do move through the files but its just really slow and is throwing my curve on backup ratios.  It looks like it affects all three servers even though one of the servers does almost nothing (its a backup) one server has a semi-high load and one has a medium load, they all pretty much backup at the same speed.  i've looked at my switch config and it says all of the boxes are running 100 Full duplex (i dont know how to check this on linux) so i'm not sure if its a config problem or a network problem.  any ideas on where to fine tune things on this?  anyone backing up redhat servers out there with some tips on increasing performance?