As anyone who has contemplated setting up an Xsan environ knows, the fibre fabric is the nervous system of the SAN. Fabric refers to all your fibre switches, cabling and HBAs (host bus adapters, the fibre channel cards in your workstations). QLogic fibre switches are Apple's recommended solution, and the manufacturer seems excited to jump into the Apple world. One feature of these switches is zoning ...
Easily configurable via QLogic's SANsurfer software, zoning is a way to control what devices or ports can communicate with each other. Devices within one zone communicate only with others in that same zone; devices can, however, participate in multiple zones at the same time.
By default the QLogic switches come with zoning turned off, and it is very possible to setup an Xsan without ever thinking about zones. But in an Xsan video production system, a first reason to use zoning may be to tighten security. You can lock down which ports on the switch are in use, to prevent any computer without an Xsan driver from plugging into the switch and doing potential damage to the SAN.
A second zoning situation appears below, where a SAN client also needs access to a dedicated storage RAID on the fabric:
(Dedicated storage in this case means that the storage is not part of the Xsan volume, it's instead just an HFS+ formatted RAID.) You can section this client and storage so they are in their own zone, preventing the other SAN clients from even seeing the volumes. And since a device can belong to multiple zones, that workstation can also be part of your SAN zone.
These are two uses for zoning in Xsans. Can anyone think of others?