Hi Erick,
Look at SAN SSO option with Backup Exec 12.5. What this will allow you to do is to share your tape library over the SAN with any other server you've configured. This makes use of the SAN speed, not your LAN, so there is no impact on local LAN traffic.
It gets configured on your backup server (licensed), and the wizard configures the system, and shares the library. On your other SAN server, you'd run the wizard and point it to your backup server. You need to run a full version of Backup Exec on every server you want to take advantage of this.
On your SAN switches, you need to zone them so that they see the HBAs in each server, which is also zoned along with the tape library. So follow your SAN switch makers best practice on this.
With this in place, you can go and install and configure the SAN SSO option.
So:
Zones:
1. Tape Library + Primary Backup Server (however many HBAs you have in order to have redundancy...so minimum 2 for 2 switches + 2 HBAs)
2. Tape Library + SAN SSO Server (as above for zones)
To read up a bit more on it, download the administrator's guide for BEWS here:
http://seer.entsupport.symantec.com/docs/308400.htm