Data Placement Based on Toleration on Twice Failures Array Codes in RAID

This paper presents an extension of the double erasure-correcting EVENODD for tolerating disk failure in highly available data storage system, which called the V codes. The V-Codes have a simple geometrical structure, namely, they can correct any double column erasure errors. In addition, the parity symbols are evenly distributed among all the columns, thus the bottleneck effects of repeated write operation are naturally overcome. We provide detailed V code´s decoding algorithms for correcting various double node failures with a geometrical structure. The complexity of encoding and decoding, the small write performance of three types of codes, are compared and analyzed, thus the V code is practically very meaningful for storage systems that need higher reliability.