is centralized backup of 7 DMZ feasible?

Dear TSMers,

We've encountered an environment which have 7 DMZ, with a total of 25 SUN
Servers (total with 250GB data) required backup. So in average, each DMZ
will require backup of 40GB data.
I'm thinking of building a dedicated backup network, say 100M Ethernet for
handling this traffic.

Solution i can think of is to build a TSM Server with 7 NIC cards, all SUN
Servers also install additional NIC card.
Also include a firewall between the TSM Server and TSM clients for security
purpose. So this will require 7 firewalls in place.

Questions
- Does anyone ever have production environment with backup of DMZ clients
that can share with me? Is it a feasible solution? I can see this will have
really big backup traffic pass through the firewall.
- Or what's the best practice in backing up servers in DMZ?
- I've heard people saying that firewall will significatly lower the
network throughput and the backup process may be unstable. Is this true?

If anyone has better solution on this, please advise. Thanks.


Best Regards,
 Molly Pui