Sector-disk (SD) erasure codes for mixed failure modes in RAID systems

Traditionally, when storage systems employ erasure codes, they are designed to tolerate the failures of entire disks. However, the most common types of failures are latent sector failures, which only affect individual disk sectors, and block failures which arise through wear on SSD's. This article introduces SD codes, which are designed to tolerate combinations of disk and sector failures. As such, they consume far less storage resources than traditional erasure codes.We specify the codes with enough detail for the storage practitioner to employ them, discuss their practical properties, and detail an open-source implementation. © 2014 ACM.