Abstract: Method and apparatus for adaptive arrangement of data on storage media, such as in a multi-device storage array across which data are stored. A virtual hot space is formed to store frequently accessed data. The virtual hot space comprises at least one hot data zone which extends across storage media of a plurality of arrayed storage devices over a selected seek range less than an overall radial width of the media. The frequently accessed data are stored to the hot data zone(s) in response to a host level request, such as from a host level operating system (OS) or by a user which identifies the data as frequently accessed data. Alternatively or additionally, access statistics are accumulated and frequently accessed data are migrated to the hot data zone(s) in relation thereto. Lower accessed data sets are further preferably migrated from the hot data zone(s) to another location of the media.

Abstract: Method and apparatus for flushing cached writeback data to a storage array. Sets of writeback data are accumulated in a cache memory in an array with a view toward maintaining a substantially uniform distribution of the data across different locations of the storage array. The arrayed sets of data are thereafter transferred from the cache memory to the storage array substantially at a rate at which additional sets of writeback data are provided to the cache memory by a host. Each set of writeback data preferably comprises a plurality of contiguous data blocks, and are preferably written (flushed) to the storage in conjunction with the operation of a separate access command within a selected proximity range of the data with respect to the storage array. A stripe data descriptor (SDD) is preferably maintained for each set of writeback data in the array.

Abstract: A management interface for a virtualized storage system including a virtualized logical disk object representing a virtual storage container, wherein the logical disk is an abstract representation of physical storage capacity provided by plurality of physical stores. A virtual disk object represents a virtual storage container. The virtual disk object is an abstract representation of one or more logical disk objects, the virtual disk object including an exposed management interface. Wherein the virtual disk object is managed through the management interface to select the one or more logical disk objects represented by the virtual disk object.

Abstract: Method and apparatus for wave flushing cached writeback data to a storage array. A cache manager operates to initiate a wave flushing operation whereby sets of writeback data in a cache memory are sequentially written to each of a plurality of logical groups radially concentric with respect to the storage medium. During the wave flushing operation, a write transducer is radially advanced across the medium in a single radial direction across boundaries between immediately adjacent groups. The write operations thus form a traveling wave across the medium, analogous to a wave in a sports stadium formed by spectators standing up and sitting down in turn. Each logical group preferably corresponds to a selected transducer seek range, such as an associated RAID stripe. Seeks are preferably bi-directional within each group, and uni-directional between adjacent groups. A dwell time (service time interval) for each group can be constant, or adaptively adjusted.

Abstract: Method and apparatus for caching and retaining non-requested speculative data from a storage array in an effort to accommodate future requests for such data. A cache manager stores requested readback data from the storage array to a cache memory, and selectively transfers speculative non-requested readback data to the cache memory in relation to a time parameter and a locality parameter associated with a data structure of which the requested readback data forms a part. The locality parameter preferably comprises a stream count as an incremented count of consecutive read requests for a contiguous data range of the storage array, and the time parameter preferably indicates a time range over which said read requests have been issued. The speculative readback data are transferred when both said parameters fall within a selected threshold range. The data structure preferably comprises a RAID stripe on a selected storage device of the array.

Abstract: An apparatus and associated method for deriving an error code value to characterize an error event that occurs during execution of an access command, memorializing the error event in an indexable error table, and logging an association of the error code value and an index in the error table related to the error event.

Abstract: Method and apparatus for caching readback data in a cache memory. Upon a transfer of cached readback data to a host device, a cache manager operates to force a retention of the readback data in the cache memory in relation to a time parameter and a locality parameter associated with said data. In this way, the readback data are either retained in hopes of satisfying a subsequent cache hit, or not retained to accommodate subsequently cached data. Preferably, the cache manager compares the time parameter to a time threshold and the locality parameter to a locality threshold, and forces said retention of the readback data if both said thresholds are met. The readback data is preferably associated with a data structure such as a RAID stripe, the time parameter preferably indicates elapsed time since last access to the structure and the locality parameter preferably indicates accesses to the structure.

Abstract: A system and method for high performance multi-controller processing is disclosed. Independent Network storage controllers (NSCs) are connected by a high-speed data link. The NSCs control a plurality of storage devices. connected by a Fiber Channel Arbitrated Loop (FCAL). To provide redundancy, for a given logical unit of storage one NSC will function as the primary controller and the other NSC will function as the primary controller and the enhance the efficiency of command-response data transfers between NSCs, mirror memory is correlated with primary memory and named resources are used for command-response data transfers. Methods are disclosed to provide for efficient active mirroring of data.

Abstract: A data storage system is provided with a pair of controllers and circuitry configured for failing back from a single active write back mode to a dual active write back mode by copying cached data directly from a cache of a survivor controller of the pair of controllers to a cache of the other controller. A method is provided for failing over from a dual active mode of first and second controllers to a single active mode of the first controller by relying on previously mirrored cache data by the second controller; reinitializing the second controller; and failing back to the dual active mode by copying cached data directly from the first controller to the second controller.

Abstract: Method and apparatus for caching readback data in a cache memory. Upon a transfer of cached readback data to a host device, a cache manager operates to force a retention of the readback data in the cache memory in relation to a time parameter and a locality parameter associated with said data. In this way, the readback data are either retained in hopes of satisfying a subsequent cache hit, or not retained to accommodate subsequently cached data. Preferably, the cache manager compares the time parameter to a time threshold and the locality parameter to a locality threshold, and forces said retention of the readback data if both said thresholds are met. The readback data is preferably associated with a data structure such as a RAID stripe, the time parameter preferably indicates elapsed time since last access to the structure and the locality parameter preferably indicates accesses to the structure.

Abstract: Method and apparatus for wave flushing cached writeback data to a storage array. A cache manager operates to initiate a wave flushing operation whereby sets of writeback data in a cache memory are sequentially written to each of a plurality of logical groups radially concentric with respect to the storage medium. During the wave flushing operation, a write transducer is radially advanced across the medium in a single radial direction across boundaries between immediately adjacent groups. The write operations thus form a traveling wave across the medium, analogous to a wave in a sports stadium formed by spectators standing up and sitting down in turn. Each logical group preferably corresponds to a selected transducer seek range, such as an associated RAID stripe. Seeks are preferably bi-directional within each group, and uni-directional between adjacent groups. A dwell time (service time interval) for each group can be constant, or adaptively adjusted.

Abstract: A data storage system is provided with a pair of controllers and circuitry configured for failing back from a single active write back mode to a dual active write back mode by copying cached data directly from a cache of a survivor controller of the pair of controllers to a cache of the other controller. A method is provided for failing over from a dual active mode of first and second controllers to a single active mode of the first controller by relying on previously mirrored cache data by the second controller; reinitializing the second controller; and failing back to the dual active mode by copying cached data directly from the first controller to the second controller.

Abstract: An apparatus and associated method for deriving an error code value to characterize an error event that occurs during execution of an access command, memorializing the error event in an indexable error table, and logging an association of the error code value and an index in the error table related to the error event.

Abstract: Method and apparatus for caching and retaining non-requested speculative data from a storage array in an effort to accommodate future requests for such data. A cache manager stores requested readback data from the storage array to a cache memory, and selectively transfers speculative non-requested readback data to the cache memory in relation to a time parameter and a locality parameter associated with a data structure of which the requested readback data forms a part. The locality parameter preferably comprises a stream count as an incremented count of consecutive read requests for a contiguous data range of the storage array, and the time parameter preferably indicates a time range over which said read requests have been issued. The speculative readback data are transferred when both said parameters fall within a selected threshold range. The data structure preferably comprises a RAID stripe on a selected storage device of the array.

Abstract: Method and apparatus for flushing cached writeback data to a storage array. Sets of writeback data are accumulated in a cache memory in an array with a view toward maintaining a substantially uniform distribution of the data across different locations of the storage array. The arrayed sets of data are thereafter transferred from the cache memory to the storage array substantially at a rate at which additional sets of writeback data are provided to the cache memory by a host. Each set of writeback data preferably comprises a plurality of contiguous data blocks, and are preferably written (flushed) to the storage in conjunction with the operation of a separate access command within a selected proximity range of the data with respect to the storage array. A stripe data descriptor (SDD) is preferably maintained for each set of writeback data in the array.

Abstract: Method and apparatus for passively mirroring data to multiple storage locations. Data are concurrently transferred by a source device to at least first and second target devices over a common pathway. Respective first and second acknowledgement signals are supplied to the source device in response to the data transfer. In some embodiments, the data are synchronously clocked into first-in-first-out (FIFO) elements of the first and second target devices using a common clock signal. In other embodiments, the data are transferred to the first device at a first rate and are transferred to the second device at a second rate different from the first rate. The source device preferably comprises a functional controller core (FCC) of a multi-device array, and the target devices preferably comprise separate buffer managers. The source device further preferably updates a metadata structure in response to receipt of the first and second acknowledgement signals.

Abstract: Method and apparatus for adaptive arrangement of data on storage media, such as in a multi-device storage array across which data are stored. A virtual hot space is formed to store frequently accessed data. The virtual hot space comprises at least one hot data zone which extends across storage media of a plurality of arrayed storage devices over a selected seek range less than an overall radial width of the media. The frequently accessed data are stored to the hot data zone(s) in response to a host level request, such as from a host level operating system (OS) or by a user which identifies the data as frequently accessed data. Alternatively or additionally, access statistics are accumulated and frequently accessed data are migrated to the hot data zone(s) in relation thereto. Lower accessed data sets are further preferably migrated from the hot data zone(s) to another location of the media.

Abstract: A storage system permits virtual storage of user data by implementing a logical disk mapping structure that provides access to user data stored on physical storage media and methods for generating point-in-time copies, or snapshots, of logical disks. A snapshot logical disk is referred to as a predecessor logical disk and the original logical disk is referred to as a successor logical disk. Creating a snapshot involves creating predecessor logical disk mapping data structures and populating the data structures with metadata that maps the predecessor logical disk to the user data stored on physical media. Logical disks include metadata that indicates whether user information is shared between logical disks. Multiple generations of snapshots may be created, and user data may be shared between these generations. Methods are disclosed for maintaining data accuracy when write I/O operations are directed to a logical disk.

Abstract: Disclosed is a data storage architecture employing a plurality of data grids each comprising an array of equal capacity data storage blocks organized into a plurality of rows and a plurality of columns such that each column corresponds to a storage domain in a data storage system and each row of the plurality of rows corresponds to a plurality of data storage blocks, one data storage block from each column of the plurality of columns at the same physical address, with the plurality of rows each having a plurality of contiguous data storage blocks in each domain. Capacity grids are produce by applying one of a plurality of sparing versions that designate at least one data storage block in each row of the grid is designated as spare, Defined within each capacity grid are one or more data storage units.

Abstract: A system and method for high performance multi-controller processing is disclosed. Independent Network storage controllers (NSCs) are connected by a high-speed data link. The NSCs control a plurality of storage devices connected by a Fiber Channel Arbitrated Loop (FCAL). To provide redundancy, for a given logical unit of storage one NSC will function as the primary controller and the other NSC will function as a mirror controller. To enhance the efficiency of command-response data transfers between NSCs, mirror memory is correlated with primary memory and named resources are used for command-response data transfers. Methods are disclosed to provide for efficient active mirroring of data.