Erasure-Coded Byzantine Storage with Separate Metadata

Although many distributed storage protocols have been introduced, a solution that combines the strongest properties in terms of availability, consistency, fault-tolerance, storage complexity and the supported level of concurrency, has been elusive for a long time. Combining these properties is difficult, especially if the resulting solution is required to be efficient and incur low cost. We present AWE, the first erasure-coded distributed implementation of a multi-writer multireader read/write storage object that is, at the same time: (1) asynchronous, (2) wait-free, (3) atomic, (4) amnesic, (i.e., with data nodes storing a bounded number of values) and (5) Byzantine faulttolerant (BFT) using the optimal number of nodes. Furthermore, AWE is efficient since it does not use public-key cryptography and requires data nodes that support only reads and writes, further reducing the cost of deployment and ownership of a distributed storage solution. Notably, AWE stores metadata separately from k-out-of-n erasure-coded fragments. This enables AWE to be the first BFT protocol that uses as few as 2t+ k data nodes to tolerate t Byzantine nodes, for any k ≥ 1.