WEAVER codes: highly fault tolerant erasure codes for storage systems

Abstract

We present the WEAVER codes, new families of simple highly fault tolerant XOR-based erasure codes for storage systems (with fault tolerance up to 12). The design features of WEAVER codes are (a) placement of data and parity blocks on the same strip, (b) constrained parity in-degree and (c) balance and symmetry. These codes are in general not maximum distance separable (MDS) but have optimal storage efficiency among all codes with constrained parity in-degree. Though applicable to RAID controller systems, the WEAVER codes are probably best suited in dRAID systems (distributed Redundant Arrangement of Independent Devices). We discuss the advantages these codes have over many other erasure codes for storage systems.