** for others who want the same answer. **
If you are already using Backup Exec, you can install the unix / linux agent onto the Snap Server 4500 and backup over the network.
I would stay away from NDMP unless you have extra money to spend on NDMP licenses, and NDMP is slower than direct attached or agent based backups.
Netvault is installed on the Snap Server, and you can get licenses and clients to backup your Windows servers using the tape attached to the Snap Server. Also, you can look at the Virtual Tape function of Netvault. The default license comes with 100Gb of Virtual Tape storage.
The idea is to backup the Windows Servers to the Virtual Tape, for quicker restores, and then move those offline to tape for long term storage. You use the Snap Server as Near Line storage and Tape as Offline storage.
You will need license from Bakbone for the Windows Servers.
So you really have 2 choices here.
1: Backup Exec with unix agent. However, an installed agent can not backup all of the Snap Servers permissions / ACLS.
2: Use Netvault for the Snap Server, which you can also backup the Windows Servers. Netvault has a custom filesystem plugin to backup the Snap Servers permissions / ACLS.
The better choice would be Netvault, with that said it is not your only choice.
The question to what devices are supported, here is a link to the supported devices: