Zoning the tape library will isolate the tape traffic to that specific zone. You must also include the backup server in the zone of course.
It is not really necessary to zone out a tape library in a fabric since a switch is point-to-point, and all end nodes only see traffic that is targeted to them. Although, if you plan to do backup during production hours by using snapshot or BCV technology, and the production servers themselves run the backup engine through the SAN, then using a third HBA zoned with the tape library is a good idea. This will prevent and tape traffic from running over the load balanced production disk HBAs.
So the answer is "it depends" on what your doing. For example, if you back up through the SAN by creating shadow images of production volumes, those volumes can then be automatically mounted to a backup server connected to the SAN. This takes the backup load off production servers. It also means you do not need a third adapter in the production servers, since all data movement is from the SAN, through the Backup server to tape.
If you are running "serverless backup," then all traffic goes directly from disk to tape through a data router instead of the backup server using the extended copy command.
So if your servers do their own backup during production hours, then use a separate tape zone which includes a dedicated backup HBA.
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