Abstract: The automated library system stores and retrieves media cartridges for an associated plurality of media drives. Within this system, a virtual robot is implemented to create multiple virtual media libraries within the single automated cartridge library system. This capability enables the use of a plurality of types of media within the single automated cartridge library and a corresponding plurality of drive elements within the library. Thus, each drive element has associated therewith a number of object storage locations within the library which contain media of a form and content that matches the drive element. The automated cartridge library system manages the correspondence between object storage location, media type, designated drive element in an automated manner such that the single library appears to the user as multiple independent libraries.

Abstract: A disk storage system that writes multiple copies of records directed to user-specified volumes. A plurality of spaced apart control units interconnected by direct data links and a corresponding plurality of sets of recording means communicate over the direct data links when a write request is received by one control unit to cause one volume in each set of recording means to write a copy of the received record.

Abstract: This system makes use of a tape cassette helical scan tape transport and 3480-type magnetic tape cartridge as the data storage media. The merging of these two incompatible elements is accomplished by the use of a novel interface that implements a "virtual tape cassette" using a tape cartridge in a manner that makes this media compatible with the tape transport. The virtual tape cassette is implemented by providing a takeup reel positioned with the magnetic tape cartridge in a relationship that substantially matches the format of a magnetic tape cassette. A short tape threading arm is used to retrieve the leader block from the tape cartridge and thread the magnetic tape over a short tape threading path to the takeup reel. Once the tape is affixed to the takeup reel, the helical scan tape guide arms transport the length of tape that is now exposed between the tape cartridge and the takeup reel to the rotary heads.

Abstract: The parallel disk drive array data storage subsystem maps between virtual and physical data storage devices and schedules the writing of data to these devices. The data storage subsytem functions as a conventional large form factor disk drive memory, using an array of redundancy groups, each containing N+M disk drives. A performance improvement is obtained by eliminating redundancy data updates in the redundancy group by writing modified virtual track instances into previously emptied logical tracks and marking the data contained in the previous virtual track instance location as invalid. Logical cylinders containing a mixture of valid and invalid virtual tracks are emptied by writing all the valid virtual tracks into a previously emptied logical cylinder as a background process.

Abstract: A peripheral device subsystem enables its peripheral devices to operate asynchronously with respect to attaches hosts through the use of managed buffers, new multiple data transfer modes, control and error recovery operations. In a preferred first or buffer mode of operation, all data of each record being transferred can be resident in a buffer before transfer to either a host or device. For a host to device write transfer, receipt of such a record by the buffer results in the subsystem signaling to the host a completion of a transfer to an addressed device even though the device has received none or only part of the data. In a second or tape write mode, recording data in a peripheral device, such as a tape recorder, completion of recording is not signaled until after the buffer has transferred the data to the recorder.

Abstract: A peripheral device subsystem enables its peripheral devices to operate asynchronously with respect to attaches hosts through the use of managed buffers, new multiple data transfer modes, control and error recovery operations. In a preferred first or buffer mode of operation, all data of each record being transferred can be resident in a buffer before transfer to either a host or device. For a host to device write transfer, receipt of such a record by the buffer results in the subsystem signaling to the host a completion of a transfer to an addressed device even though the device has received none or only part of the data. In a second or tape write mode, recording data in a peripheral device, such as a tape recorder, completion of recording is not signaled until after the buffer has transferred the data to the recorder.

Abstract: A peripheral subsystem, such as a tape storage subsystem, assigns logical and physical values to blocks of signals received from a host. A host can retrieve such values for use later to locate the blocks of signals and for error recovery purposes. In a buffered peripheral subsystem, such values define current signal transfer status of the buffer.

Abstract: Reels of magnetic tape used in a reel-to-reel drive system suffer from an inter-layer slip if the reel has gone through environmental changes. This slip will cause errors to occur in the reading of the tape, since a constant tension and velocity and an accurate position is required in the reel-to-reel drive. To check whether the tension of the tape needs to be refreshed, the end of the tape is firmly held while the hub is driven in a reverse direction against the firmly held end of the tape. A detected reverse rotation indicates an inter-layer slip condition. The tape tension must be refreshed by unreeling the tape and rereeling with the correct tension applied. The reel of tape is then ready for operation.