Stable disk performance with non-sequential data block placement

Abstract

General purpose file systems traditionally use sequential data block allocation policies, which by reducing disk head seek and rotational latency increase disk access performance. However, these methods also directly expose the variable data transfer rate of modern multi-zone disks, resulting in unstable and non-predictable disk throughput depending on the files being accessed. In this paper, we present the Zone-Round-Robin (ZRR) block allocation policy which avoids this problem by distributing the data blocks of a file over the entire disk to achieve near constant file access rates. Experimental results show that ZRR leads to stable disk performance independently of the set of files being used and that the data throughput achieved is close to the average disk performance.