We have one that uses three (3).
Two fast ethernet & one GB.
You have to remember that your standard TCP/IP routing is what determines
how these boxes talk !
Client traffic will go in which ever interface you point to and will return
out to the client based on standard routing in the system (but will go back
to the ip in the received packets).

Back when we built our environments "SAN" wasn't really around so we built a
sudo-SAN.  Works great !

Our busiest S70 TSM server (just 2 processors & 1 GB memory) seems to max
out at about 60-ish GB/hr of inbound  compressed client data  (actually kind
of hard to find enough clients to push more than that ;-) but I need to
check recent #'s )
        (so during DB backups, that is about 240 GB/hr of client file spaces
being  backed up)

Is this good or bad ? ? ?
It is just what we see and it serves our needs !

Dwight