Abstract: A method is described which provides various new data storage system capabilities by using data storage structures within industry standard (or other pre-existing) formats used with data recording devices employing removable media. The data storage structures used by the present method comprise formats which contain regions previously marked as "contents of this region are not of interest" or marked as "no data was recorded within this region". These data storage structures are thus transparent to present data recording devices so as not to disrupt their data processing functions. However, the data storage structures are available to be used by new data recording devices (or old devices that have been updated) so that new data embedded therein may be used to enhance the functionality of the system which utilizes the data storage structures.

Abstract: A data storage subsystem dynamically maps a virtual data storage device image presented to associated processors to physical data storage devices used to implement the data storage subsystem. Multiple destage memory elements are concurrently active to increase an aggregate destage data transfer rate and to allow data to be stored on various memory elements appropriate to the type of data contained in each stored virtual object. An open logical cylinder list is used to maintain data integrity among multiple open destage memory elements. Memory elements are also selected to function as archive memory. The data storage subsystem includes a plurality of data storage elements configured into at least two redundancy groups, each redundancy group including n+m of the data storage elements, and a cache memory connected to the redundancy groups and a host processor interface.

Abstract: The control software and hardware in the tape drive control unit creates and manages a header segment at the beginning of the magnetic tape. This header is interposed between a leader portion of the magnetic tape on the 3480-type cartridge and the remainder of the magnetic tape contained therein. This header segment contains two sections, a first of which is a data record directory that is used by the control unit to denote the location of each data record written on to the magnetic tape as well as administrative information associated with the data record. The second section of the header is an administrative information section that contains data relating to the magnetic tape itself.

Abstract: This method provides new data storage capabilities that are implemented within the industry standard formats of mountable media data recording devices. The new data storage structures are written into regions presently marked on the mountable media as "contents of this region are not of interest" or marked as "no data was recorded within this region". These data storage structures are transparent to present data recording devices and do not disrupt their data processing functions. However, the data storage structures are available to new data recording devices so that new data embedded therein is used to enhance the functionality of the system which utilizes these data storage structures. The types of embedded data may include ECC (error correction codes), tape position information, audit information, security information, mount history, media defect history, authentication notation, generation-identification notation, etc.

Abstract: Data storage elements that present uniform external dimensions but contain media of varying types and characteristics provide variable data storage and/or recording characteristics. To differentiate between the various media that can be housed within the common form factor, each data storage element is equipped with a leader block having a leader block slot uniquely dimensioned to correspond to the media contained within the data storage element. The leader block slot can be engaged by a mounting pin section on any of a plurality of mounting pins in a media drive.

Abstract: A cassette for a high performance tape drive is disclosed. A cassette shell having the same general external dimensions as an industry standard leader block tape cartridge (3480/3490) includes both a tape supply spool and a take-up spool. Two tape guides present a segment of tape to a cassette access port which can be closed by a sliding door to prevent contamination when the tape is not in use. A tape cleaning device and a spool locking device are incorporated into the cassette mechanism.

Abstract: In response to the mounting of a magnetic tape on the tape drive, the tape drive begins reading data from the tape into the preload buffer while concurrently signalling the data processor that the tape drive is instantaneously available to read/write data. The data processor can then begin the data transfer operation without incurring the delay occasion by media set up time. The data that is transferred from magnetic tape is stored in the preload buffer in anticipation of the data processor issuing a data read command. Upon receipt of the data read command, the tape drive reads the data out of the preload buffer to the data processor via the data channel while simultaneously reading data from the magnetic tape into the preload buffer.

Abstract: A performance optimized computer data recording media format and associated control logic method is disclosed. Localized data block recording, such as by concurrent parallel or serpentine recording techniques, is used to create a series of Virtual Volumes on a single physical volume. Physical localization of data blocks records is achieved which tends to minimize access time. Using the Virtual Volume construct, other industry standard data storage systems can be emulated. Many data storage operations requesting physical motion are translated into virtual motion which in turn results in significantly less physical motion than that requested, thereby reducing access times and media and drive apparatus wear.

Abstract: A pair of operationally independent disk drive array data storage subsystems are used to emulate one or more physical devices shared between two control modules. The storage control units of the two data storage subsystems are interconnected by at least one data link to exchange control and data signals therebetween. The storage control units of both data storage subsystems are synchronized to maintain identical virtual device images of certain assigned virtual devices both of the data storage subsystems wherein the duplicated data records of the single virtual device are stored. The data records are therefore stored in available memory on both of the two data storage subsystems. Data is exchanged over the data link to maintain consistency of the two sets of mapping tables.

Abstract: The removable media management system operates with a manual, an automated, or a combination of subsets of manual and automated library system to store and retrieve media cartridges for an associated plurality of drive elements. This system enables the use of a plurality of types of media within the single monolithic cartridge library system and a corresponding plurality of drive elements associated with said library system. Thus, each drive element has associated therewith a number of object storage locations within the library system which contains media of a form and content that matches the drive element. The removable media management system maps the correspondence between object storage location, media type, designated drive element in a manner such that the single library is partitioned into subsets for the user, i.e.

Abstract: The 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 subsystem functions as a conventional large form factor disk drive memory, using an array of redundancy groups, each containing N+M disk drives. This system copies data records by simply creating a duplicate data record pointer in a virtual track directory to reference the original data record. This enables the host processor to access the data record via two virtual addresses while only a single physical copy of the data record resides in the data storage subsystem.

Abstract: The control software and hardware in the tape drive control unit creates and manages a multiple level error detection and correction system to protect the data written on the magnetic tape. The helical scan data write circuits operate on the received stream of data records to produce two orthogonal error detection and correction codes on a scan group level. The data write circuit divides the received stream of data records into data segments, each of which contains a predetermined number of data bytes. A first of these scan group error codes is generated on a per data segment basis while a second scan group error is generated across multiple data segments. A third level error correction code is also used to protect an entire scan group rather than data on a per byte basis. The third level error correction code generator produces an error code over a predetermined number of sequentially written scan groups to enable the control unit to reconstruct an entire scan group if its data integrity is compromised.

Abstract: This magnetic tape cartridge has the same exterior dimensions as a conventional 3480-type magnetic tape cartridge but houses different media. To clearly identify the media contained in the cartridge, a label receiving recess in included on the back of the cartridge. A human readable and machine readable label can be inserted into this recess to identify the media contained in this cartridge. Additional label recesses are provided juxtaposed to the media identification recess and on the top and side of the cartridge to receive user installed labels to uniquely identify the cartridge.

Abstract: The multiple step data read apparatus provides a buffer memory (108-0) for each read/write head (110-0) in the rotating media (111-0) data storage system that can store up to the entire track (400) of data that includes the requested data (Sectors 2-6). The data is fragmented such that the data transferred into the read/write head buffer first is transmitted to the control unit first whether or not that data is at the beginning of the data requested by the control unit. The data is further fragmented such that critical portions of the data are available to the control unit to satisfy the host request as soon as the data is read from the device. This fragmenting results in the data becoming available to the control unit in the minimum time possible and the performance of the subsystem being the maximum possible.

Abstract: The control software and hardware in the tape drive control unit creates and manages a header segment at the beginning of the magnetic tape. This header is interposed between a leader portion of the magnetic tape on the 3480-type cartridge and the remainder of the magnetic tape contained therein. This header segment contains two sections, a first of which is a data record directory that is used by the control unit to denote the location of each data record written on to the magnetic tape as well as administrative information associated with the data record. The second section of the header is an administrative information section that contains data relating to the magnetic tape itself. The stream of data records is divided into data segments, a plurality of which comprise a single helical scan track. The helical scan tracks are formed into scan groups and written on the magnetic tape.

Abstract: Data storage elements that present uniform external dimensions but contain media of varying types and characteristics provide variable data storage and/or recording characteristics. To differentiate between the various media that can be used within the common form factor, each data storage element is equipped with a leader block, the tape threading slot of which is uniquely dimensioned to correspond to the media contained within the data storage element.

Abstract: The universal data storage element presents a uniform form factor data storage element but enables the user to vary the contents to include a selection of media types or miniaturized drive elements used therein to provide variable data storage and/or recording characteristics. This enables the user to use multiple types of media in an automated library system or a manually operated media storage and retrieval system, since the form factor of all of the data storage elements contained therein is uniform. The use of the universal data storage element provides the capability of varying the data storage capabilities of the data storage element to be consistent with the data recording technique used therein. This capability enables the user to use a diversity of drive elements connected to the computer system without having to have a corresponding diversity in media element handling systems.

Abstract: The use of a dynamically mapped virtual memory system permits the storage of data so that each data record occupies only the physical space required for the data. Furthermore, the data storage subsystem manages the allocation of physical space on the disk drives and does not rely on the file extent defined in the count key data format. Data compaction apparatus is provided to remove the gaps contained in the stream of count key data records received from the host processor. A data compression algorithm is then used to compress the received data into a compressed format for storage on the disk drives. It is the compacted, compressed data that is finally stored on the disk drives. Furthermore, any data record received from the host processor absent data in the user data field therein is simply listed in the virtual memory map as a null field occupying no physical space on the disk drives.

Abstract: The parallel disk drive array data storage subsystem dynamically maps between virtual and physical data storage devices and schedules the writing of data to these devices. The data storage subsystem functions as a conventional large form factor disk drive memory, using an array of redundancy groups, each containing N+M disk drives. The data storage subsystem does not modify data stored in a redundancy group but simply writes the modified data as a new record in available memory space on another redundancy group. The original data is flagged as obsolete. A mapping table is maintained to identify portions of these redundancy groups which contain newly written or modified virtual track instances. These marked virtual track instances are written to backup medium as a background process and the mapping table is updated to clear the flags that identify these virtual track instances as having been modified.

Abstract: The deleted dataset space release system provides facilities in a dynamically mapped virtual memory data storage subsystem to immediately release the physical space occupied by a deleted dataset for use by the data storage subsystem to store subsequently received data files. This system also provides data security by preventing the unauthorized access to the data of scratched data files, both in cache memory and on the data storage devices. The deleted dataset space release system utilizes a user exit in the host processor data file scratch routine to transmit information to the data storage subsystem indicative of the host processor data file scratch activity. Existing channel command words are used in a manner that is transparent to the host processor. The data storage subsystem thereby immediately receives an indication that the host processor is scratching a data file from the volume table of contents of a virtual volume.