Abstract: On-line storage devices are migrated to new storage devices in a non-disruptive manner. A host executing multipath I/O software is initially coupled to a source storage device via at least one active path. The target storage device is configured with the source device's device identification information. The target storage device is coupled to the host via a passive path so that the target storage device can return its device identification information to the host but cannot respond to I/O read or I/O write requests from the host. All paths between the host and the source storage device are then disconnected. An on-line data migration session between the source storage device and the target storage device is then activated. The path between the target storage device and the host is then re-configured from passive to active so that the target storage device can respond to I/O read and I/O write requests.

Abstract: A partitioned storage subsystem includes a plurality of directors, each having at least one processor thereon, each of the directors acting as one of: a primary director and a secondary director for a subset of logical devices handled by the partitioned storage subsystem, where primary directors actively perform I/O operations for logical devices and wherein secondary directors receive data to mirror memory of a corresponding primary director. The partitioned storage subsystem also includes a global memory distributed among the plurality of directors, where a different portion of the global memory is provided on each of the directors, and includes metadata for the logical devices, provided in the global memory, where the metadata contains information that correlates logical device data with physical device data. The physical device data may be provided by at least one disk drive coupled to at least one of the directors.

Abstract: A storage array includes a plurality of directors, each having at least one processor thereon and a global memory distributed among the plurality of directors. A different portion of the global memory is provided on each of the directors. A interconnect fabric is coupled to each of the directors. Global memory accesses performed by one director to access memory of another director through the interconnect fabric. The storage array also includes a plurality of partitioned storage subsystems, each including a separate subset of the directors, where each of the partitioned storage subsystems handles I/O operations for a plurality of logical devices independently of I/O operations for logical devices of other ones of the partitioned storage subsystems, the I/O operations using metadata provided in the global memory of the corresponding directors and containing information that correlates logical device data with physical device data.

Abstract: Handling I/O operations for a storage array includes distributing metadata among separate memories of a plurality of directors of the storage array, where the metadata correlates logical device data with physical device data. A first one of the directors receives an I/O operation for a particular logical device. Handling I/O operations may also include determining which of the plurality of directors contains metadata corresponding to the particular logical device, and, in response to the metadata being on a different one of the directors, the first director providing a request to the different one of the directors. The directors may be interconnected by an interconnect fabric. The first one of the directors may provide a request to the second one of the directors via the interconnect fabric. Determining which of the plurality of directors contains metadata correspond to the particular logical device may include using a lookup table.

Abstract: A system for de-duplicating data includes providing a first volume including at least one pointer to a second volume that corresponds to physical storage space, wherein the first volume is a logical volume. A first set of data is detected as a duplicate of a second set of data stored on the second volume at a first data chunk. A pointer of the first volume associated with the first set of data is modified to point to the first data chunk. After modifying the pointer, no additional physical storage space is allocated for the first set of data.

Abstract: Described are techniques for detecting incompatibilities. A first contents of a data item is determined in accordance with a first set of conventions associated with a first processor architecture. A second contents of said data item is determined in accordance with a second set of conventions associated with a second processor architecture and including at least one convention that is not included in said first set. An actual difference between the first contents and the second contents is determined. It is determined whether the actual difference is expected. If the actual difference is not expected, the data item is flagged as an incompatibility candidate. Code referencing the data item is examined to determine any coding incompatibilities due to coding dependencies.

Abstract: Described are techniques for performing data recovery processing for two failed devices included in a set of devices. It is determined whether the two failed devices are each one of the data devices, a horizontal parity device, or a diagonal parity device. Each of the data devices is partitioned into N?1 data segments. The horizontal parity device includes N horizontal parity segments each including parity information for a horizontal grouping of N?1 of the data segments. The diagonal parity device includes N diagonal parity segments each including parity information for a diagonal grouping of N?1 of the data segments. Recovery processing is performed to recover two failed devices in accordance with the diagonal parity device, the horizontal parity device, and the data devices.

Abstract: Described are techniques for selective data replication. Cached data is replicated if it is characterized as critical. Critical data may include data associated with a write I/O operation. Cache locations are selected for replicated data so that a first location is mapped to a first memory board and a second location is mapped to a second memory board. Data for a read operation is not replicated in cache. Other non-cache data that is critical and thus replicated includes metadata. Cache locations for data of read and write I/O operations are selected dynamically at the time the I/O operation is made from the same pool of cache locations.