A director is essentially a very high reliability multi-port Fibre Channel fabric switch. Typically it offers at least 32 ports with any-to-any connectivity so any devices on the switch can be connected to each other device in a non-blocking manner. Directors also have no single point of failure. All critical components in a director are redundant and will automatically fail over. In addition, directors are designed to allow upgrades and code revisions without shutting down the unit. While directors are expensive, typically 2 to 2.5 times more than the equivalent number of ports on Fibre Channel switches, they are worth considering for mission-critical applications where access to data must be maintained at all cost. Manufacturers of directors also claim their units have lower installation costs because fewer boxes and less cabling is required and lower on-going costs because they are easier to manage.
Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.