Abstract: A first computer is adapted to communicate with another computer and to a redundant storage subsystem external to the first computer. The first computer comprises memory comprising state information and a processor that receives a state from another computer. The received state is indicative of whether the other computer may perform write transactions to the redundant storage subsystem. The first computer's processor also determines whether to perform a data merge operation on the redundant storage subsystem based on the other computer's last received state prior to a failure of the other computer.

Abstract: In accordance with at least some embodiments of the invention, a system comprises a plurality of computers coupled together and to an array of redundant storage devices that is accessible to the plurality of computers. Each of the plurality of computers comprises a local memory that stores at least one bitmap. The least one bitmap logs regions of the redundant array that have been modified.