HV Code: An All-Around MDS Code to Improve Efficiency and Reliability of RAID-6 Systems

The increasing expansion of data scale leads to the widespread deployment of storage systems with larger capacity and further induces the climbing probability of data loss or damage. The Maximum Distance Separable (MDS) code in RAID-6, which tolerates the concurrent failures of any two disks with minimal storage requirement, is one of the best candidates to enhance the data reliability. However, most of the existing works in this literature are more inclined to be specialized and cannot provide a satisfied performance under an all-round evaluation. Aiming at this problem, we propose an all-round MDS code named Horizontal-Vertical Code (HV Code) by taking advantage of horizontal parity and vertical parity. HV Code achieves the perfect I/O balancing and optimizes the operation of partial stripe writes to continuous data elements, while preserving the optimal encode/decode/update efficiency. Moreover, it owns a shorter parity chain which grants it a more efficient recovery for one disk failure. HV Code also behaves well for the degraded read operation and accelerates the process to reconstruct two disabled disks by executing four recovery chains in parallel. The performance evaluation demonstrates that HV Code well balances the I/O distribution and eliminates up to 27.6% and 32.4% I/O requests for partial stripe writes operation when compared with RDP Code and HDP Code. Moreover, compared to RDP Code, HDP Code, X-Code and H-Code, HV Code reduces up to 5.4%~39.8% I/O requests per element for the single disk reconstruction, decreases 6.6%~28.3% I/O requests for degraded read operations, and achieves the same efficiency of X-Code for double disk recovery by shortening 47.4%~59.7% recovery time compared with other three codes.