As stated at the introduction to this appendix, round-trip production can range from a single user working with multiple applications on the same computer, all the way up to a large group of editors and engineers accessing vast amounts of data in a shared storage environment. Any facility with two or more artists creating content under the same roof is perfect for workgroup collaboration of this sort because productivity increases exponentially when multiple users can access the very same media. No time wasted copying files; less chance of errors from revision-naming conventions. Investments in hardware can be recouped sooner when the storage is centralized, simply because the storage can be dynamically allocated wherever it is needed most.
A storage area network, or SAN, is designed for exactly this type of collaboration. A SAN is a network whose primary function is to link multiple storage systems to multiple desktop workstations. Typical SANs today operate on 2-gigabit-per-second fiber channel cabling connected through one or more multi-port fiber channel switches. One of the best features of a properly designed SAN is that the storage volume can be scaled dynamically as the production workload increases, without users' ever having to take the network offline or reboot administrative systems. Xsan is in this class. It is what's referred to as an enterprise-class (that is, large-facilities-that-can't-afford-the-slightest-bit-of-downtime), high-performance SAN file system. It runs on Mac OS X and is compatible with systems running on a selection of qualified non-Apple SAN client seats.
Like the best enterprise-class SANs, Xsan includes a metadata controller that acts like a network traffic cop. Whenever any user on the network wants to read or write to a file, the user's computer asks the SAN traffic cop for permission to proceed. Xsan's metadata controller software includes a "failover" provision, which means that these traffic cop duties are automatically handed over to another computer in the event the first controller should fail for whatever reason. The whole point of built-in protections like failover and multi-pathing (where a second cable is used if the first is cut) is to ensure that the network is operational and the media and project files on the SAN volumes are available to all users all the time.
Storage area networks offer the promise of tremendous increases in creativity and productivity not unlike those of the networked office environment where multiple users have simultaneous access to the Internet and printers. Apple's pro apps, and the level of round-trip production they provide, are ideally suited for use in a centralized storage, collaborative workgroup environment supported by Xsan.