Seneca: Remote Mirroring Done Write

Abstract

Remote mirroring is widely deployed, but its complexities are surprisingly poorly understood. This means that data is less well protected than it ought to be, and possible optimizations are infrequently taken advantage of. To address these difficulties, we (1) demystify the design space by presenting a taxonomy of the approaches in use, (2) describe Seneca – a new asynchronous remote-mirroring protocol that supports write coalescing, asynchronous propagation, and in-order delivery, and (3) report on a performance and correctness validation of Seneca. We are confident that the result is a robust remote-mirroring protocol that provides good performance and predictable behavior in the face of a wide range of failure types, such as rolling disasters. 1