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 ). 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...