Abstract: A data storage system (100) and a method of storing data are described including a cache (118) with a variable number of levels (210, 220, 230, 240). Each level in the cache (118) has a cache controller (212, 222, 232, 242) and a cache memory (214, 224, 234, 244) for storing data. An address mapping is recorded and applied between each of the levels of the cache (118). The address mapping corresponds to a point in time virtual copy operation such as a snapshot copy operation applied to the cache (118) and enables point in time virtual copy operations to be carried out in electronic time. A new level is created in the cache (118) when a point in time virtual copy operation is received by the cache and a corresponding address mapping is applied to the previous level in the cache (118).

Abstract: An improved design for a high density thin film inductive write head assembly is provided. A pedestal and back flux closure of ferromagnetic material are formed on opposite ends of a planarized first pole piece. A plurality of coils of conductive material are deposited on top of the first pole piece between the pedestal and back flux closure. The coils comprise a plurality of loops or turns having voids between the coil loops. A photo resist material is deposited in the voids between the coils and the back flux closure, which is hard baked. A layer of alumina is deposited over the coils and hard baked photo resist material. The pedestal, back gap, coils, photo resist, and alumina are planarized by using a chemical mechanical polishing process. The thickness of the photo resist material relative to the coils is reduced using an O2 reactive ion etching process. A hard carbon or alumina filler is applied to fill the gaps between the coils and the photo resist.

Abstract: A memory array system is provided comprising a plurality of rows of memory cells, each row having an address, wherein each memory cell stores volatile data requiring periodic refreshing. A refresh controller controls the periodic refreshing of data in each row of memory cells. A refresh address counter indicates the address of the row of cells for refreshing. A temporary data storer is used for storing data from the memory cell indicated for refreshing. A data inverter inverts data from the memory cell indicated for refreshing. A comparator associated with the temporary data storer and the data inverter compares data in those devices. An indicator bit is associated with the refresh address counter to indicate whether the data stored in the address indicated by the refresh address counter is inverted.

Abstract: The present invention provides a depopulation version hard disk drive apparatus that has a reduced number of magnetic heads and suspension arms from a standard hard disk drive apparatus, wherein the magnetic head can still be properly controlled during a loading state. The hard disk drive apparatus includes a ramp which interfaces with the suspension arm when loading and unloading the arm. An angle of a second slope surface 61c of the ramp in the depopulation version hard disk drive is set larger than that of the corresponding slope surface of the ramp 6 the a standard version hard disk drive.

Abstract: A system and method are provided that reduce the amount of data held commonly in both high-ranking and low-ranking cache memories, thereby having each of those cache memories hold data more efficiently. More particularly, a computer system is provided with an HDC card 21 connected to an expansion bus 20 and an HDD unit 22 connected to the HDC card 21. The HDC card 21 is provided with a disk cache (high-ranking cache memory) and the HDD unit 22 is provided with a disk cache 54 (low-ranking cache memory). The HDC card 21 and the HDD unit 22 exchange select information for selecting a swap mode of each cache memory when the system is started up, thereby selecting different swap modes according to the exchanged select information respectively.

Abstract: A staging method and means for both device read and update write operations in which messages and commands between a storage subsystem and a fixed-block formatted RAID array emulating a variable-length record (CKD) formatted device for both read and write operations are evaluated to ascertain whether the record addressing was random and truly in record mode. If they are in that mode, then partial track staging by the RAID array control from the fixed-block formatted HDDs to a subsystem cache or the like would reduce device contention by reading and staging less than full track.

Abstract: A transducer suspension system has a transducer head, layered member, and a load beam. The layered member is comprised of a support layer, an electrically insulating layer, an electrically lead base layer, and an electrically conducting layer. The electrical leads are formed from the combination of the base layer and electrically conducting layer. The resulting electrical leads are both flexible and highly conductive.

Abstract: The present invention provides a digital filter which is capable of preventing filter outputs from being discontinuous when a filter characteristic is changed. Initially, a servo assistant (SA) computes parameters for computing servo data, and based on the computed parameters, the SA judges an operating mode. If the mode has been changed, the SA will advance in processing. Next, the parameters of a filter are changed in correspondence with the judged operating mode, and the initial values of the interior variables of the filter are set to appropriate values.

Abstract: A reference current and resistance is used to determine a reference voltage. A variable current is then applied to the MR read head, and is adjusted to produce a voltage equal to that of the reference voltage. Then, the known current and voltage is used to determine the resistance of the MR read head.

Abstract: A storage system is provided for storing data for a computer system where the storage capacity can be incrementally increased without disrupting the operations of the storage system. The storage system comprises a base unit, and a plurality of modular units. The modular units are inserted into the system as increased storage capacity is required. Each modular unit has an enclosure comprising top, bottom, and side walls. The bottom and top walls each have at least one power connector and data transmission connector. The bottom wall of a first modular unit enclosure attaches to the base unit enclosure and the top wall of the first modular unit enclosure can attach to the bottom wall of a second modular unit enclosure. At least one back plane is provided in each modular unit for providing attachment for a set of storage devices.

Abstract: In a storage system comprising an array of storage devices, including a processor and memory, a plurality of logical tracks are organized on the storage devices in segments comprising columns striped across the storage devices. A system and method are provided for storing logical tracks in the storage devices. Sequentially logically related logical tracks are stored together in neighborhoods. Logical tracks of the same neighborhood A0 destaged at the same time are assigned to a single open segment with other logical tracks of the same neighborhood type. The time at which open segments are designated as closed segments to be written to the storage devices is based on performance, disk utilization and memory utilization criteria. Logical tracks are never split between segment columns. Also, attempts are made not to split a neighborhood of logical tracks being destaged together between segment columns.

Abstract: Each of HDDs 6 and 7 is partitioned into two drives, comprising an outer zone and an inner zone. Each outer zone having a faster read/write access rate is called the “faster portion”, whereas each inner zone having a slower read/write access rate is called the “slower portion”. In accordance with a control program in RAM 3, CPU 1 is caused to execute “mirroring” such that the faster portion of one of HDDs 6, 7 is paired with the slower portion of the other one of HDDs 6, 7. In so configuring, it is possible to execute “mirroring” such that a difference between the access rates of the faster zone of one of the disks and the slower zone of the other one of the disks is always kept large. Thus, whenever one of the disks having a faster access rate becomes ready earlier, it is possible to immediately start the next read/write to this disk without waiting for completion of the write to the other disk having a slower access rate, thereby to improve access efficiency.

Abstract: A method and system in accordance with the present invention provides additional addressable space on a disk for use by a host processor using a virtual data storage subsystem. The method and system includes defining at least one of a plurality of extended image devices on a disk and requesting an instant image to be addressed to an extended image device utilizing channel command words by a host processor. The method and system also includes reading the instant image utilizing commands, such as channel command words or common descriptor blocks, by the host processor. In a method and system in accordance with the present invention, a plurality of extended image devices are defined as extensions of a primary functional device. Data may be transferred between at least one of the plurality of extended images and the primary functional device, or between at least one of the plurality of extended image devices and another of the plurality of extended image devices.

Abstract: A method and apparatus for managing update writing in place in linear address space mapped memories. This is attained by partitioning the memory into compressed and uncompressed areas, estimating the percent of compressible images of fixed-length symbol strings recordable into the image locations, revising the estimate upward or downward as a function of the persistency of runs of writes to one area or the other, and adjusting the relative number of locations in the areas proportionally to the revised estimate.

Abstract: In a storage system comprising an array of storage devices including a processor and memory, a plurality of data blocks are organized on the storage devices in segments striped across the storage devices. A main directory, stored in memory, contains the location on the storage device of each of the data blocks. For each segment a segment directory having information on the data blocks in the segment is stored on the storage devices. When a damaged segment directory is detected, a checkpoint of the main directory is written to the storage devices. A list is maintained of damaged segment directories such that segments on the damaged segment directories list are not garbage collected. Following a main directory recovery procedure, the damaged segment directories are reconstructed using the main directory.

Abstract: A storage system is provided for storing data for a computer system where the storage capacity can be incrementally increased without disrupting the operations of the storage system. The storage system comprises a base unit, and a plurality of modular units. The modular units are inserted into the system as increased storage capacity is required. Each modular unit has an enclosure comprising top, bottom, and side walls. The bottom and top walls each have at least one power connector and data transmission connector. The bottom wall of a first modular unit enclosure attaches to the base unit enclosure and the top wall of the first modular unit enclosure can attach to the bottom wall of a second modular unit enclosure. At least one back plane is provided in each modular unit for providing attachment for a set of storage devices.

Abstract: A staging method and means for both device read and update write operations in which messages and commands between a storage subsystem and a fixed-block formatted RAID array emulating a variable-length record (CKD) formatted device for both read and write operations are evaluated to ascertain whether the record addressing was random and truly in record mode. If they are in that mode, then partial track staging by the RAID array control from the fixed-block formatted HDDs to a subsystem cache or the like would reduce device contention by reading and staging less than full track.

Abstract: A method and means for performing logical-combining functions such as XOR operations in a RAID 3 or 5 array or a combinational configuration of disk drives. The logical combining occurs below the device attachment interface and is used in generating new parity for write update operations and data rebuilding. Each disk drive is modified to use a segmented and address synchronized buffer in the write and read paths, and a logical circuit that combines the data in the write path before buffering with the data in the read buffer as it is read out from the buffer. The logically combined result is presented at the device read path interface. The combined data from a first disk drive interface is introduced into the write path of a second path through the second device interface and the logical combining repeated ad seriatim, the device interfaces being connectable in a daisy-chain manner and configurable by array controller commands.

Abstract: A system and method are provided for coordinating command for updating and reconstructing data in an array of storage devices connected to a computer system when multiple initiators issue commands. Sets of data blocks and corresponding parity blocks are arranged on a plurality of storage devices, such that a data block can be reconstructed using a set of data blocks and at least one parity block. When a new data block is written to the disk drive, a corresponding old parity block is write updated with an updated parity block. When reconstructing an unavailable data block an initiator issues a read command to each storage device having a data block or a parity block used for reconstructing the unavailable data block. Each read command is enqueued on a command queue for each storage device in a priority order coordinating each read command with any write update command for the same block so that a new data block and an old parity block are not read as part of the same parity stripe and vice versa.

Abstract: A method is described for operating a data processing system having a plurality of processors to sort a set of data records each having an associated key for governing the sort process. The method comprises determining a range for the key values by sampling the key values. The range is divided into a plurality of quantiles, one for each processor, each quantile having a respective index. At each processor, a plurality of buckets are defined, each bucket corresponding to a respective one of a plurality M.sub.p of subintervals in the quantile, each subinterval having a respective index. The index of the quantile in which the key value lies and the index of the subinterval in which the key value lies are determined directly from the key values using fast operations. Each key is distributed to the processor corresponding to the quantile in which the key value lies.