I have lots of data that will be backed up across servers and I don't want this affecting the performance of my websites and stuff I have happening specifically on other nic devices so is it possible to specify which nic I want to do the backups on?
I guess you're using different networks then? The backup will then happen over the NIC that is in the same network as the backup server.
I don't understand why you have multiple NICs on the same network? Are you talking about real NICs or virtual ones?