Patent ID: 8103903

Claim:
A method of maintaining data storage reliability in a write-back distributed data storage system including multiple nodes, each node comprising an array of failure independent data storage devices, the method comprising: storing information as a set of stripes, each stripe including a collection of multiple data strips and associated parity strips, the stripes distributed across multiple corresponding primary data nodes and multiple corresponding parity nodes; a primary data node maintaining the data strip holding a first copy of data, and each parity node maintaining a parity strip holding a parity for the multiple data strips; performing a read-modify-write parity update protocol for maintaining parity coherency, a primary data node driving parity coherency with its corresponding parity nodes, independently of other data nodes, in order to keep its relevant parity strips coherent; during a preparation phase, upon a node failure, a lowest survivor node in a forward sequence driving an abort sequence for the read-modify-write parity update protocol; and during a commit phase, upon a node failure, the lowest survivor node in the forward sequence driving a restart of the commit phase for the read-modify-write parity update protocol.