APS: adaptable prefetching scheme to different running environments for concurrent read streams in distributed file systems

Distributed file systems (DFSs) are widely used in various areas. One of the key issues is to provide high performance of concurrent read streams (i.e., multiple series of sequential reads by concurrent processes) for their applications. Despite the many studies on local file systems (LFSs), research has seldom been done on concurrent read streams in DFSs with different running environments (i.e., different types of storage devices and various network delays). Furthermore, most of the existing DFSs have a sharply degraded performance compared with a LFS (i.e., EXT4). Therefore, to achieve high performance in concurrent read streams, this study introduces a populating effect that keeps sending subsequent reads to a storage server and then proposes an adaptable prefetching scheme (APS) to obtain the effect even in different running environments. Hence, our APS resolves all the problems that we identified as dramatically degrading the performance in existing DFSs. In three different types of storage devices and in various network delays, the evaluation results show that our prefetching scheme (1) achieves almost the same performance as a LFS from an individual server and (2) minimizes the performance degradation of random reads.