Fault tolerant architectures for continuous media servers

A continuous media server that provides support for the storage and retrieval of continuous media data at guaranteed rates using one of two fault-tolerant approaches that rely on admission control in order to meet rate guarantees in the event of a failure of the data storage medium that renders part of the continuous media inaccessible. In the first approach, a declustered parity storage scheme is used to uniformly distribute the additional load caused by a disk failure, uniformly across the disks. Contingency bandwidth for a certain number of clips is reserved on each disk in order to retrieve the additional blocks. In the second approach, data blocks in a parity group are prefetched and thus in the event of a disk failure only one additional parity block is retrieved for every data block to be reconstructed. While the second approach generates less additional load in the event of a failure, it has higher buffer requirements. For the second approach, parity blocks can either be stored on a separate parity disk, or distributed among the disks with contingency bandwidth reserved on each disk.