LaRS: A Load-Aware Recovery Scheme for Heterogeneous Erasure-Coded Storage Clusters

To reduce the probability of data unavailability, it is extremely important to quickly recover failed data in a (k+r, k) erasure-coded storage cluster. In practice, storage nodes in a large-scale storage system have various network bandwidths and I/O capabilities, therefore, the heterogeneity of storage systems increases along with the growing scale. Both traditional recovery scheme and Fastest recovery scheme simply retrieve k surviving blocks from k surviving nodes, thereby resulting in low recovery performance in a heterogeneous storage cluster. In this paper, we propose a Load-aware Recovery Scheme (Lars) for heterogeneous RS-coded storage clusters. Lars not only takes into account both the heterogeneity and load of nodes, but also enables all surviving nodes to service reconstruction reads. The amount of surviving blocks retrieved by a surviving node depends on its load weight which is determined by both network bandwidth and I/O capacity. More blocks are fetched from faster nodes, and vice versa. The three recovery schemes are implemented on a 9-node heterogeneous RS-coded storage cluster, where a set of comparative experiments are conducted. The experimental results show that our Lars scheme outperforms the other two schemes by a factor of up to 1.58.