Abstract: A cache storage system and method are provided for saving storage space in a cache, the system and method for use in a data storage system having multiple storage devices and multiple virtual addresses, each virtual address having a data object associated therewith. Each data object is stored at a storage device location having a unique identifier. The cache storage system and method include a cache for storing a data object associated with at least one virtual address. For a first virtual address, the first virtual address data object is staged into the cache. For a second virtual address, a pointer is generated for use in pointing to the first virtual address data object staged in the cache when the storage device location identifier of the second virtual address data object matches the storage device location identifier of the first virtual address data object.

Abstract: A client-directed pre-stage operation of a cache memory used to access data blocks from a mass data storage device attached to a host computer through a channel control processor is provided by a method and apparatus comprising a channel control processor for retrieving data blocks from the mass storage device to be pre-staged within the cache memory, a channel interface coupled between the channel control processor and the host computer, a mass storage device interface coupled between the channel control processor and the mass storage device, and a cache memory coupled between the channel interface and the mass storage interface; the cache memory is further coupled to the cache control processor to provide the cache control processor access to data stored within the cache memory. The cache control processor receives a cache bitmap from the host computer to specify the data blocks from the mass storage device to be pre-staged into the cache memory.

Abstract: A client-directed pre-stage operation of a cache memory used to access data blocks from a mass data storage device attached to a host computer through a channel control processor is provided by a method and apparatus comprising a channel control processor for retrieving data blocks from the mass storage device to be pre-staged within the cache memory, a channel interface coupled between the channel control processor and the host computer, a mass storage device interface coupled between the channel control processor and the mass storage device, and a cache memory coupled between the channel interface and the mass storage interface; the cache memory is further coupled to the cache control processor to provide the cache control processor access to data stored within the cache memory. The cache control processor receives a cache bitmap from the host computer to specify the data blocks from the mass storage device to be pre-staged into the cache memory.

Abstract: Systems and methods are provided to backup, restore and relocate compressed data images, e.g., DASD compressed tracks, associated with virtual storage volumes. A compressed track image of the data is first stored in a storage volume. The data derives from a connected host connected with a control unit that manages the storage volume. When the host data is uncompressed, the control unit compresses the data. In backup, the host reads the compressed data with a read protocol and the control unit assigns metadata to the compressed track. The compressed track is then stored in a backup device, e.g., a tape drive. In restore, the host writes the compressed track to the control unit with a write protocol. If desired, the track is relocated to a different location or to a different storage volume through the associated metadata. In decompression, a seed value is assigned to the data to ensure identification across relocation.

Abstract: A system and method for synchronizing a data copy that include a source volume having a data file stored thereon, the source volume for receiving write commands from a host, executing the write commands to generate an updated data file, and generating a record of the write commands. The system and method further include a secondary volume having a copy of the data file stored thereon, the secondary volume for receiving and storing data indicated by the write command record, wherein the copy of the data file and the data indicated by the write command record are available for use in generating a copy of the updated data file.

Abstract: A system and method for synchronizing a data copy include in one embodiment first and second remote copy trios, each with source, target, and secondary volumes. Source volumes store initial data files, execute write commands to generate updated data files, and generate records of the write commands. Target volumes receive copies of the initial data files and the write command records, and transmit the copies of the initial data files and data indicated by the write command records to secondary volumes. Secondary volumes store the copies of the initial data files and the data indicated by the write command records, which are available for use in generating copies of the updated data files. The target volumes transmit to the secondary volumes in series relative to each other so that consistency is maintained at all times across the source volumes.

Abstract: A cache storage system and method are provided for saving storage space in a cache, the system and method for use in a data storage system having multiple storage devices and multiple virtual addresses, each virtual address having a data object associated therewith. Each data object is stored at a storage device location having a unique identifier. The cache storage system and method include a cache for storing a data object associated with at least one virtual address. For a first virtual address, the first virtual address data object is staged into the cache. For a second virtual address, a pointer is generated for use in pointing to the first virtual address data object staged in the cache when the storage device location identifier of the second virtual address data object matches the storage device location identifier of the first virtual address data object.

Abstract: A system and method for synchronizing a data copy that include a source volume having a data file stored thereon, the source volume for receiving write commands from a host, executing the write commands to generate an updated data file, and generating a record of the write commands. The system and method further include a secondary volume having a copy of the data file stored thereon, the secondary volume for receiving and storing data indicated by the write command record, wherein the copy of the data file and the data indicated by the write command record are available for use in generating a copy of the updated data file.

Abstract: A system and method for synchronizing a data copy include in one embodiment first and second remote copy trios, each with source, target, and secondary volumes. Source volumes store initial data files, execute write commands to generate updated data files, and generate records of the write commands. Target volumes receive copies of the initial data files and the write command records, and transmit the copies of the initial data files and data indicated by the write command records to secondary volumes. Secondary volumes store the copies of the initial data files and the data indicated by the write command records, which are available for use in generating copies of the updated data files. The target volumes transmit to the secondary volumes in series relative to each other so that consistency is maintained at all times across the source volumes.

Abstract: The invention provides for remote copying, between peer storage systems, with data extent granularity. A compressed data image is read from a first location of a primary storage volume. Metadata, and then the compressed data image, are transferred to a secondary storage volume. The metadata specifies a first location within the primary storage volume and a second location within the secondary storage volume. The compressed track is then stored into a second location of the secondary volume. A host connected to the primary control unit specifies data extents within the primary and secondary volumes. The data extents specify the first and second locations, and more preferably define cylinder information, track information, and start and end addresses. An “Establish Pair” command can be used to specify the data extents. A seed value can be used with the metadata to identify the data image during subsequent decompression of the data image in the secondary storage volume.

Abstract: Systems and methods are provided to backup, restore and relocate compressed data images, e.g., DASD compressed tracks, associated with virtual storage volumes. A compressed track image of the data is first stored in a storage volume. The data derives from a connected host connected with a control unit that manages the storage volume. When the host data is uncompressed, the control unit compresses the data. In backup, the host reads the compressed data with a read protocol and the control unit assigns metadata to the compressed track. The compressed track is then stored in a backup device, e.g., a tape drive. In restore, the host writes the compressed track to the control unit with a write protocol. If desired, the track is relocated to a different location or to a different storage volume through the associated metadata. In decompression, a seed value is assigned to the data to ensure identification across relocation.

Abstract: The cache buffer management system functions in a mass storage subsystem to locate a less recently referenced cache buffer to be overwritten with new data. The system of the present invention utilizes P in-cache bitmaps (ICBMs) in a history table to indicate that a particular cache buffer, corresponding to each bit of each ICBM, has been referenced during the past P time periods. A cache buffer is "hot" if the corresponding bit in any of the P ICBMs indicates that the cache buffer has been referenced. Otherwise, where all corresponding bits in all P ICBMs are clear, a cache buffer is "cold". In conjunction with the ICBMs, a track reference count list (TRCL) circular list contains the ID of cache buffers in chronological order of their reference. To determine a buffer suitable for overwriting, the cache buffer management system searches backward from oldest toward newest in the TRCL list of references to find a cache buffer which is "cold". The first "cold" cache buffer found is then overwritten with new data.

Abstract: The cache memory space in a computer system is controlled on a dynamic basis by adjusting the low threshold which triggers the release of more cache free space and by adjusting the high threshold which ceases the release of free space. The low and high thresholds are predicted based on the number of allocations which are accomplished in response to I/O requests, and based on the number of blockages which occur when an allocation can not be accomplished. The predictions may be based on weighted values of different historical time periods, and the high and low thresholds may be made equal to one another. In this manner the performance degradation resulting from variations in workload caused by prior art fixed or static high and low thresholds is avoided. Instead only a predicted amount of cache memory space is freed and that amount of free space is more likely to accommodate the predicted output requests without releasing so much cache space that an unacceptable number of blockages occur.