Abstract: Parity updates are performed in an efficient manner after data is modified on removable media in a RAID or RAIL array, within or outside the array, without requiring that all of the data on all of media in a parity group be read. Instead, a list is maintained identifying those blocks of data were which modified on the media. Only the corresponding blocks on the remaining media in the parity group are read to calculate the new parity. Alternatively, a list can be maintained identifying the bits which were changed on the media. Consequently, only the corresponding bits of the parity block(s) need be changed.

Abstract: A high resolution, independent position sensor is provided, having application in a magnetic tape drive and other environments in which a linear or angular position is to be monitored. Analog outputs from an inexpensive, low resolution optical encoder are processed to correct gain and offset distortions and are used as the basis for an interpolation process. If a code strip having a 127-micron grating is used, a resolution of about 0.125 microns can be achieved.

Abstract: A disk storage unit according to the present invention comprises a disk for storing data, a head for at least reading data stored on the disk, a controller for controlling a seek operation in which the head moves from a current track to a target track and a tracking operation in which the head tracks the target track after reaching the target track, based on a tracking error signal, and a device for adding a dc offset to the tracking error signal so that head drive power having a direction opposite that of the seek operation and corresponding to the velocity of the head in the seek operation is generated after the head has reached the target track and the seek operation has been switched to the tracking operation.

Abstract: When an automated data storage library includes the capability of storing and accessing more than one media type, it is necessary for the library manager to keep track of what media type is associated with each volume serial number ("VOLSER"), and where each is physically located in the library. For efficiency, VOLSERs will be grouped in sequential ranges, each range associated with a single media type (although a particular media type can be associated with different, non-contiguous ranges). When the number of VOLSERs and ranges is small, new ranges can be easily added, and existing ranges can be easily deleted or modified, manually by a system administrator. However, when the number of VOLSERs and ranges becomes large, it becomes burdensome for the administrator to track the VOLSER ranges and media types. An automated VOLSER range management system is provided which detects whether a new or modified range overlaps or is adjacent to an existing range with the same media type.

Abstract: An apparatus and method are provided for detecting and correcting data stream misalignments during read back of data in an optical drive unit. In a dual PLL system, after a data stream is divided into separate positive and negative data streams, correlations are made between the transitions in the even nibbles of a sync mark and the transitions in the odd nibbles. Proper and improper alignments can be detected. The resync marks are also employed to determine whether the two data streams are misaligned and, if they are, by how much. While the position of an alignment bit within a resync mark can be detected, realigning the data streams based upon this position can result in small defects causing false alignment and a continuous error until the next resync. Consequently, the present invention employs other bits in the resync mark and in the adjoining customer data field to validate the misalignment independent of the alignment bit itself.

Abstract: One or more stationary bar code readers are provided in an automated storage library to monitor the movement of magazines, cartridges and/or disks within the library and to maintain an updated inventory on the location of each item in the library. Preferably, a reader is positioned at the head of each column of storage cells and at the front of each drive unit. Each magazine and cartridge has a linear bar code label and each bare disk has a concentric bar code label. Each label is fixed to a surface visible to the readers whereby, as a magazine, cartridge or disk is passed in front of a reader, the label is read, decoded and the information used to update a library inventory table.

Abstract: The present invention provides a retainer system of an automated storage and retrieval system, or library, which prevents information storage elements, or cartridges, from escaping from their respective storage cells when the entire library is transported from one location to another. The retainer system comprises a retractable cable, a null, or dummy, cartridge, and an array of storage cells. One end of the retractable cable is attached to the null cartridge and the other end of the cable is affixed to one end of the array of storage cells. Initially, the null cartridge is positioned in a storage cell located adjacent to the end of the storage array where the cable is affixed. When all the information storage elements are placed inside their respective storage cells within the array, the null cartridge is moved from its original position to a storage cell at the opposite end of the storage array.

Abstract: In an automated storage and retrieval library system, a library controller is directed to examine a command queue, as well as the state of the grippers and the state of the data drive units. In general, upon completion of the examination, the controller determines whether an additional command, currently in the queue, can be executed in conjunction with (that is, before, during or after) execution of the current command, thereby optimizing the utilization of the accessor. For example, if the accessor is to execute an exchange command, a move command might be in the queue which requires moving a cartridge from the area in which the accessor will be located after the exchange is made but before the exchanged cartridge is moved to a new location. In such an event, the controller will direct that the move command be overlapped with the second half of the exchange command by using the empty gripper.

Abstract: An optical disk recorder employs laser drive signals having diverse current or power levels. A scaling digital-analog-converter (DAC) supplies a scaled reference signal to a plurality of scaled DACs. The scaled DACs supply the diverse laser drive signals. Calibrating the scaling DAC calibrates the scaled DACs. A base array of DACs include not only the scaling DAC but a plurality of base array DACs. Such base array DACs control reading operations as well as supplying a threshold current. The threshold current is that laser drive signal current level below which laser 25 does not emit a laser beam. During writing, the CUT current is added to the laser drive currents supplied by the scaled DACs. A desired CUT current is determined by calculating a slope of the laser drive current to emission of radiation. Then the slope is extrapolated to a zero emission point below which no coherent emission of radiation occurs.

Abstract: The present invention provides an apparatus and method for initializing a magnetic tape when it is mounted in a tape drive. In one embodiment, each time a tape is mounted, control parameters pertaining to the servo system are set to predetermined values and servo read elements in the tape head are activated. The tape is moved and a number of position error signal (PES) samples are read and averaged for each of the active servo elements. The value of one or more of the parameters is modified and new PES readings and averages are obtained. This process is repeated for a predetermined combination of parameter values whereupon read and write offsets are calculated and stored for each servo element. During an actual read (or write) operation, the tape head is positioned relative to the data tracks on which the desired data is located and servo control enabled.

Abstract: In an automated information storage and retrieval library system having a single recording drive, a backup or copying operation is preferably performed in a single-threaded fashion whereas in a library having two or more drives, a multi-threaded approach is preferred. The present invention provides a library with the capability to back up information from one piece of media to another in an adaptive fashion. A determination is made whether there is one drive unit available in the library or whether at least two are available. A multi-threaded backup approach is employed if there are two available recording drives in the library and a single-threaded approach is employed if there is only one available drive. In addition to making the determination when a copy request is received, the library controller can make the determination at various stages of a copy operation and adaptively change between single-threaded and multi-threaded approaches.

Abstract: Methods for recording information onto CD-Recordable and CD-Erasable optical disks are provided. In a first embodiment, after a session or packet of data is recorded, it is verified to detect unrecoverable errors. If no such errors are present, the session or packet is fixed and recording ends. If an unrecoverable error is detected, the session or packet is re-recorded in an area of the disk immediately following the originally recorded area. When the recorded data is verified as being readable, the session or packet is fixed by recording lead-in and lead-out areas on the disk and by updating a table of contents with the location of the verified data and not the originally recorded data. In a second embodiment, the data is checked as it is recorded. If a defect is suspected, recording halts and the presence of the defect is verified. If a defect is present, the data is re-recorded in an area of the disk immediately following the originally recorded area.

Abstract: An optical disk player reads either thin-substrate disks or thick-substrate disks. The disk players optical system is designed for reading the thin-substrate optical disks and has an effective numerical aperture. Thick-substrate optical disks having a thicker substrate than the thin-substrate optical disk result in the laser beam reading such thick-substrate optical disks having spherical aberration sufficient to prevent reliable data detection. When thick-substrate optical disks are being read, the read portion of the optical system is automatically changed to accommodate the undesired spherical aberration. The thick-substrate disk reflected laser beam is subjected to annular filtering that reduces spherical aberration sufficiently for enabling data and servo signal detection. Annular filtering is provided in an optical read path by an effective opaque or translucent disk centrally located in a pupil of the laser beam optical filter disposed in the read portion.

Abstract: A laser calibration apparatus and method first calibrates a maximum laser power level. Then lesser laser power levels are calibrated. A separate calibration pattern is used for calibrating each of the laser power levels. The calibration patterns used for the lesser laser power levels include the calibrated maximum laser power level. Such inclusion established a fixed relationship between the maximum laser power level and all of the lesser laser power levels. The calibration is performed on an optical disk, preferably of the magneto optical type. The calibrated laser power levels are then used to record pulse-width modulated signals.

Abstract: An interlock system is provided for removable-media drive unit to prevent the drive loader from attempting to pull in and mount a data cartridge before it is released by a mechanical gripper or human hand. The interlock system includes a light source and a photodetector positioned in front of the drive on opposite sides of the path cartridge takes when it is being inserted or removed from the drive loader. The presence of the cartridge, gripper or other object in the path interrupts a light beam from the light source thereby signalling the drive controller to disable the drive loader. When the gripper has released the cartridge and withdrawn, or when the path is otherwise clear, the photodetector again detects the light beam and signals the drive controller that the loader can be safely enabled. In one embodiment, the light source and photodetector are mounted on a card which plugs into the face of the drive.

Abstract: A data storage system includes a data storage medium, such as a magnetic tape, that has a first control data storing area or drive partition that is addressable only by a peripheral drive mounting the medium and a plurality of other addressable data storing partitions for storing data. A volume table of contents may be stored in one of the addressable partitions. A tachometer measures and indicates physical locations on the storage medium. Each of the partitions have an extent on the storage medium indicated by said physical locations. The control data in the drive partition includes directories of medium control blocks, such as tape marks, defect marks and the like; directory of all addressable partitions including the physical locations at the beginning of each partitions and other medium physical and logical parameter data. A so-called mount-demount medium control block in the drive partition indicates a demount status that shows all data stored in the drive partition is valid.

Abstract: A single accessing mechanism is deployed adjacently to two optical media libraries. Each library has a plurality of record medium storage compartments arranged respectively into a one-compartment wide column. Each library has its own media drive (player or recorder). An accessing module in the accessing mechanism is movable along the column lengths. The accessing module has two transfer compartments respectively for transferring record media in respective ones of said libraries between the respective storage compartments and the respective media drives. The compartments, either in the accessing module or the library, are vertically offset. A vertical space between vertically adjacent record media enables a fetching apparatus to simultaneously enter such space in both libraries. Moving the accessing module upward or downward respectively selects the record medium to be fetched--in only one of the two libraries.