The present invention relates to automated data storage libraries for storing and retrieving cartridges with data storage media therein, for use by data processing apparatus having access to such libraries.
Automated data storage libraries provide a data storage environment in which large quantities of data are distributed between a plurality of discrete data storage elements, such as magnetic tape or optical disk cartridges, which are placed in addressable storage cell locations arranged in one or more storage cell banks. The storage elements are accessed using positionable cartridge picker mechanisms which may include one or more selectively activatable cartridge grippers.
In order to transport a data storage element between storage cell locations, one of which may contain a data read/write unit in communication with a host data processing system, a picker mechanism is first positioned at a source storage cell containing a data storage element to be retrieved. A gripper is activated to engage the storage element and retract it from the storage cell. The picker mechanism is then positioned at a destination cell and the gripper is again activated to insert the storage element in the storage cell and release it. In some data storage libraries, it is desirable to employ two or more grippers in a single picker mechanism. Using multiple grippers minimizes picker travel because plural data storage elements can be transported simultaneously. Moreover, a picker mechanism that accesses two opposing storage cell banks on either side of the picker mechanism preferably utilizes a gripper for each bank.
A disadvantage of prior art, multiple gripper picker mechanisms is that discrete gripper drive systems are used to control gripper positioning. This requires a duplication of hardware components and associated control system support functionality. The result is increased complexity and cost, as well as reduced response time due to increased picker mass caused by hardware and control system redundancy.
Accordingly, an evident need exists for an automated data storage library having multiple gripper picker capability but without the attendant disadvantages of multiple gripper drive systems. What is required is a system of reduced complexity and cost in which data storage and retrieval times are effectively minimized.