The Raid-6 Liber8Tion Code

James S. Plank, EECS Department, University of Tennessee.

The International Journal of High Performance Computing Applications, Volume 23, Number 3, pages 242-251, 2009. DOI: 10.1177/1094342009106191

The official home page of this paper from SAGE publications, The conference precursor to this paper.


Large centralized and networked storage systems have grown to the point where the single fault tolerance provided by RAID-5 is no longer enough. RAID-6 storage systems protect k disks of data with two parity disks so that the system of k + 2 disks may tolerate the failure of any two disks. Coding techniques for RAID-6 systems are varied, but an important class of techniques are those with minimum density, featuring an optimal combination of encoding, decoding and modification complexity. The word size of a code has an impact on both how the code is laid out on each disk's sectors and how large k can be. Word sizes which are powers of two are especially important, since they fit precisely into file system blocks. Minimum density codes exist for many word sizes with the notable exception of eight. This paper fills that gap by describing a new code called The RAID-6 Liber8tion Code for this important word size. The description includes performance properties as well as details of the discovery process.

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