Vector Locally Repairable Codes With Small Repair Bandwidth and Small Sub-Packetization Levels

Abstract

Maximum distance separable (MDS) codes in distributed storage systems provide the optimal tradeoff between fault tolerance and storage overhead. As a kind of MDS codes, minimum storage regenerating (MSR) codes have attracted a lot of attention since they are also optimal in terms of repair bandwidth. However, MSR codes suffer from a high repair degree, meaning many helper nodes are needed in the node repair process. Compared to MSR codes, locally repairable codes (LRCs) can significantly reduce the repair degree at the cost of increased storage overhead. The recently introduced concept of vector LRCs combines the advantages of MSR codes and LRCs, providing a tradeoff between repair degree/repair bandwidth and storage overhead. Most existing vector LRCs are built on MSR codes or their shortened versions. However, existing MSR codes have an unavoidably large sub-packetization levels, which also result in large sub-packetization levels in the corresponding vector LRCs. In this paper, we propose a new vector LRC structure, where MDS array codes (without shortening) can be employed as the local codes. Based this new structure, we propose three constructions of vector LRCs with small sub-packetization levels and small repair bandwidth, whose required field sizes are comparable to the code lengths. Additionally, the first two constructions offer a flexible tradeoff between the sub-packetization level and the repair bandwidth, while the third construction has a sub-packetization level of 2, making it easy to implement. Compared to existing vector LRCs, the new vector LRCs provide significantly smaller sub-packetization levels and support a wider range of parameters.