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LibraryXpress consists of three modules: the GCM (Global Control Module), which contains the brains of the library, allowing it to integrate the other units, as well as a 16-cartridge capacity; the Base Module, which can hold one or two DLT drives and 10 cartridges; and the Capacity Module, which houses 16 cartridges. You can start simple, with a one-drive Base Module and its attendant 10-cartridge magazine. And as you grow, you can add a second DLT drive and begin bui lding up your rack to handle truly large-scale backup.

Once you outgrow a Base Module, you can add one GCM and any combination of the Base and Capacity Modules. Overland employs a twofold connectivity strategy to glue the various modules. To shuttle cartridges among the modules, the DLT LibraryXpress uses an "Xpress" channel that can be lengthened to support as many modules as you add, up to a maximum of nine. The Xpress channel, a single cartridge shuttle, takes cartridges from the module's robotics and moves them up or down the rack to the next module's robotic arm. This is carried out via a clever--and nearly invisible--back door on the modules.

Control of the modules from the GCM's LCD panel is achieved via eight serial connectors on the back of the GCM. By relying on individual connections, the GCM can simultaneously control each module; that means that a failed or busy unit won't get in the way of messages between the GCM and one of its slave modules.

Cartridges are housed in pull-out trays tha t can be accessed by pressing an unlock/open button. Other tray-based libraries require you to use a front-panel key. Still, we're not all that enamored of the tray approach. Removing and loading trays is a clumsy affair. In particular, the 16-tape tray on the GCM is unwieldy and difficult to manipulate, especially when it's full of tapes. Equally annoying is that you have to press the open/unlock button to open the door that closes when you remove or insert tape trays. Balancing a tray while pushing a button and waiting for the door to open is awkward, at best.

Another problem with the tray approach, as it's implemented here, is you cannot directly access the drives. Getting at individual drives would require you to disconnect the unit, pull it from the rack and enter the service-technician zone by opening the entire enclosure.

Trays aside, although the GCM takes over control from the Base Module, you can still control individual Base Modules from the GCM's or that Base Module's operator control panel s. One particularly important feature lets you designate a module (Base or Capacity) to serve as a "mailbox," letting you load cartridges from a centralized location. You use the Base Module's panel primarily for loading and unloading cartridges, while the GCM's panel duplicates all the functions of the Base Module. Rather than taking the library offline manually, you can enter the control menu to automatically take the library offline. From there you can do almost everything--move cartridges around the library, clean drives, set SCSI IDs and run diagnostics.

At $30 per gigabyte, LibraryXpress offers exceptional value. When you factor in the savings generated by the scalability of this product, the picture changes to one of superior economy. There isn't any amount of data that can't be served by a LibraryXpress configuration.