Efficient and Modular Consensus-Free Reconfiguration for Fault-Tolerant Storage

Quorum systems are useful tools for implementing consistent and available storage in the presence of failures. These systems usually comprise of a static set of servers that provide a fault-tolerant read/write register accessed by a set of clients. We consider a dynamic variant of these systems and propose FreeStore, a set of fault-tolerant protocols that emulates a register in dynamic asynchronous systems in which processes are able to join/leave the set of servers during the execution. These protocols use a new abstraction called view generators, that captures the agreement requirements of reconfiguration and can be implemented in different system models with different properties. Particularly interesting, we present a reconfiguration protocol that is modular, efficient, consensus-free and loosely coupled with read/write protocols. An analysis and an experimental evaluation show that the proposed protocols improve the overall system performance when compared with previous solutions