Abstract: A magnetic tape drive simultaneously senses on a magnetic tape three evenly spaced-apart servo track areas for servoing a multi-track magnetic head to follow a concurrent set of data tracks on the magnetic tape. The data tracks are arranged into a plurality of track groups. Each track group has a first and second subgroup of data tracks. The first subgroup of tracks are scanned in a first relative motion of the magnetic tape and magnetic head as a forward direction (tape is being spooled from a supply tape reel). The second subgroup of tracks are scanned in a second relative motion of the magnetic tape and magnetic head that is opposite in direction to the first relative direction and is a forward direction of scanning. While writing data in any one of the plural track groups, a servo dropout affecting most of the servo track areas is detected and indicated as a servo error. Writing is aborted. The relative position of the magnetic tape and head is detected at both longitudinal ends of the servo dropout.

Abstract: A tape drive data storage apparatus incorporates a system for dynamically anticipating and resolving potential data error conditions. The system performs read and/or write data transfer operations on a tape medium, during which time it generates a track performance database representing a map of potential data error conditions occurring on the tape. As operations continue, determination is made from the track performance database whether one or more track fallout thresholds have been reached in one or more regions of the tape. If so, an error recovery bellcord action is performed to minimize the occurrence of data error conditions.

Abstract: Information bearing signals are recorded in one of a plurality of record formats on one record medium, such as a magnetic tape, magnetic disk, optical disk, and the like. The format selected may be commanded or based upon record lengths, in bytes. When the record length equals or exceeds a predetermined number of bytes, then one record is recorded in each signal block of the record format. When the record length is less than the predetermined number, then a second format is used which inserts several of the records in one of the signal blocks. The signal block and its packets respectively contain indications of formats such that any one of several formats may be used on one record medium and in one signal block having a plurality of variable length packets. Logical indicators, such as format marks, tape marks, and the like, may separate formats used on the storage medium.

Abstract: Information bearing signals are recorded in one of a plurality of record formats on one record medium, such as a magnetic tape, magnetic disk, optical disk, and the like. The format selected may be commanded or based upon record lengths, in bytes. When the record length equals or exceeds a predetermined number of bytes, then one record is recorded in each signal block of the record format. When the record length is less than the predetermined number, then a second format is used which inserts several of the records in one of the signal blocks. The signal block and its packets respectively contain indications of formats such that any one of several formats may be used on one record medium and in one signal block having a plurality of variable length packets. Logical indicators, such as format marks, tape marks, and the like, may separate formats used on the storage medium.

Abstract: A tape drive data storage apparatus incorporates an error recovery system that is dynamically controlled to perform knowledge-based error recovery in accordance with a novel error recovery method. As the tape drive apparatus performs read and/or write data transfer operations on a tape medium loaded in the tape drive, an error recovery knowledge base is generated representing a tape map of ECC error correction locations on the tape medium. If error recovery is initiated and it is determined from the tape map that one or more error clustering thresholds have been reached in one or more selected regions of the tape medium, appropriate error recovery action is taken depending on whether a data read or data write operation is underway. If read (or write) data is being processed, the error recovery procedures performed by the error recovery system can be selectively modified in the affected tape medium regions to address the expected cause(s) of the data error.

Abstract: Information bearing signals are recorded in one of a plurality of record formats on one record medium, such as a magnetic tape, magnetic disk, optical disk, and the like. The format selected may be commanded or based upon record lengths, in bytes. When the record length equals or exceeds a predetermined number of bytes, then one record is recorded in each signal block of the record format. When the record length is less than the predetermined number, then a second format is used which inserts several of the records in one of the signal blocks. The signal block and its packets respectively contain indications of formats such that any one of several formats may be used on one record medium and in one signal block having a plurality of variable length packets. Logical indicators, such as format marks, tape marks, and the like, may separate formats used on the storage medium.

Abstract: Information bearing signals are recorded in one of a plurality of record formats on one record medium, such as a magnetic tape, magnetic disk, optical disk, and the like. The format selected may be commanded or based upon record lengths, in bytes. When the record length equals or exceeds a predetermined number of bytes, then one record is recorded in each signal block of the record format. When the record length is less than the predetermined number, then a second format is used which inserts several of the records in one of the signal blocks. The signal block and its packets respectively contain indications of formats such that any one of several formats may be used on one record medium and in one signal block having a plurality of variable length packets. Logical indicators, such as format marks, tape marks, and the like, may separate formats used on the storage medium.

Abstract: A peripheral data storage system employing a data buffer connected to a plurality of data storage devices, such as tape recorders, dynamically reallocates data buffer storage segments among the various data storage devices. A normalized elapsed-time period is established based upon the number of accesses to the data storage devices. When the number of accesses reaches a threshold the need for dynamic reallocation is examined. During the elapsed-time period the system monitors which of the allocated buffer segments have any data transfer activity at all and also measures the intensity of the activity for the respective buffer segments. In a peripheral system, the intensity is indicated by the number of channel command retries submitted to a connected host processor for the respective allocated buffer segment. Based upon the allocation status of the buffer segments and intensity of activities of the respective buffer segments, the buffer allocations are selectively reallocated among the data storage devices.

Abstract: Data transfers between respective buffer segments and data source-sinks, such as peripheral data storage devices, are scheduled as a series of transfers based upon most recent, next most recent, to the least recent usage of the buffer segments by a utilization device. A list of segments ordered by such usage is dynamically maintained. Replacement of segment allocations among devices proceeds from the least recently used, next least recently used, etc. to the most recently used segments. Therefore a single list controls replacement and read ahead (prefetch) of data from devices to the buffer and transfer of data from the buffer to the devices, all based on utilization of the buffer by the utilization device.

Abstract: Data transfers between a host processor and a peripheral data recorder in a peripheral data storage system, such as tape recorder peripheral data storage system, are via a random-access buffer store in the peripheral data storage system and interposed between the peripheral data recorder and the host processor. A command queue storage in the peripheral data storage system stores commands received from the host processor for the peripheral data recorder. Additionally, apparatus in the peripheral data storage system form commands for transferring data between the peripheral data recorder and the buffer store without intervention of the host processor; both read transfers (data transfer from the peripheral data recorder to the host processor) and write transfers (data transfer from the host processor to the peripheral data recorder) are enabled via the formed commands.

Abstract: Data processing workloads are balanced between a plurality of data processing units, such as control units of a peripheral system, based upon tallies of data processing delays. The workloads are arranged in work allocations, such as assignment of peripheral devices to a control unit; a separate delay tally is kept for each work allocation along with a summation of all delays in each control unit. When a tally threshold in any data processing unit is exceeded, load balance is examined. Upon a predetermined imbalance, a work allocation having a delay tally equal to a mean value of the different delay summations is transferred to a data processing unit having a lower delay summation.