A leaner, more efficient, available copy protocol

Available copy protocols provide the highest data availability and data reliability of all replication protocols that do not regenerate failed replicas. Unfortunately, all existing implementations of available copy protocols either rely on complex procedures for ascertaining which replicas are up to date after a total failure or have to wait for the recovery of all failed sites. We present a simple technique for efficiently implementing the available copy protocol. Our protocol does not require version numbers and maintains only n+log(n) bits of state per replica. We also show under standard Markovian assumptions that our new protocol provides the same data availability as the best feasible implementations of the available copy protocol.