Abstract: A high performance data path for performing XOR on the fly. A first memory is connected to a first bus and a second memory is connected to a second bus selectively coupled to the first bus. Logic for performing an XOR can be switched into connection with the first and second bus for XORing data in a buffer with the data passed from one of the memories to the other memory. The result is replaced into the buffer to permit successive XORing. When reading from an interrelated group of disks such as a RAID 3 group, the data path permits an N-1 and go mode in which a read does not wait for data from the last disk to retrieve its data sector. If the last disk contains data (as opposed to parity) the data is obtained from the XORed data in the XOR buffer of the high performance data path. For writing data, the XOR on the fly generates the parity sector for writing at the completion of a write to an interrelated group of disks.

Abstract: A recovery method for use in a data storage system in which a plurality of data storage devices are connected to each of two communication paths. A switch may route requests to either of the two communication paths. With one data storage controller in communication with the data storage devices over a first path and a second data storage controller in communication with the data storage devices over a second path, upon detection of a malfunction on the first path, a data storage controller may request access to the other path. Thereafter, the controller may be switched into connection with the remaining operable path so as to share that path with the other controller.

Abstract: A recovery method and fail-over switch for use in a data storage system in which a plurality of data storage devices are connected to each of two communication paths. The switch may route requests to either of the two communication paths. Switching may be accomplished by two fail-over switches connected to each other and each in connection with one of the two communication paths. With one data storage controller in communication with the data storage devices over a first path and a second data storage controller in communication with the data storage devices over a second path, the fail-over switches may be used upon detection of a malfunction on one path to switch a controller into connection with the remaining operable path so as to share that path with the other controller.