A portable canister for upgrading, converting, or servicing an automated data storage library includes an assembly with cartridge cells. The portable canister is mounted within a data storage drive compartment, and/or another slot within the automated data storage library. The storage capacity of the library may be increased by adding portable storage canisters. When occupying a data storage drive slot, the portable storage canister may be removed and replaced with a data storage drive. Dual accessor library expansion may be simplified by using the portable canister as a test canister in the service bay of the library. Any library frame or storage module may become the service bay simply by inserting a test canister into the frame or storage module. This eliminates the need to shut down the library and reconfigure the frames to relocate the service bay.