The MiniLibrary Expansion Unit assumes control over all attached TL891DLX modules, allowing for the creation of a multi-module virtual library in a single rack mount configuration. It also provides an additional 1.28TB (with 2:1 compression) of capacity (no drives). The Expansion Unit supports up to (5) five additional modules in a single rack mount configuration. With the use of a special included pass-through mechanism, all tapes within this multi-module configuration are available to all DLT drives, making a single virtual library.This true scalability of performance and capacity allows the end user the opportunity to configure the device to meet their specific requirements, as well as offers a "pay as you grow" solution for easy capital management. The multi-unit configuration can also be disassembled at any time and each module redeployed independently to meet changing corporate backup strategies.