Abstract: A multi-nodal data processing system in which each node has a local memory for storing message send vectors, one for each other node in the system. When a node has a message to send, it places the message in the message send vector corresponding to the destination node of that message. When a node is ready to receive messages, it reads messages from the message send vectors corresponding to this node in the other nodes. Each message send vector has a head pointer and a tail pointer for defining the head and tail of a queue of messages. Each tail pointer is held locally, in the same node as the message send vector to which it relates, while the head pointer is held in the destination node of that message send vector.

Abstract: A RAID system includes an array of disk units, with data mapped on to the disks as a series of stripes, each containing data and parity chunks. The data chunks of each stripe are located on radially more outer parts of the disks and the parity chunks of each stripe are located on radially more inner parts of the disks. As a result, the amount of head movement for read operations is reduced, which improves the read performance. Successive chunks within each stripe are physically located at successively more radially inward positions on successive disks, so that each stripe has a helical configuration. Mirroring can be considered as a special case in which the number of data chunks is equal to the number of parity chunks, and the parity consists of a simple replication of the data. In this case, data is written to the outermost half of a first disk and to the innermost half of a second disk, and is read from the first disk.