Ordering disks for double erasure codes

摘要

Dish arrays have been designed with two competing goals in mind, the ability to reconstruct erased disks (reliability), and the speed with which information can be read, written, and reconstructed (performance). The substantial loss in performance of write operations as reliability requirements increase has resulted in an emphasis on performance at the expense of reliability. This has proved acceptable given the relatively small members of disks in current disk arrays. We develop a method for improving the performance of write operations in disk arrays capable of correcting any double erasure, by ordering the columns of the erasure code to minimize the amount of parity information that requires updating. For large disk arrays, this affords a method to support the reliability needed without the generally accepted loss of performance.