Tuning of striping units in disk-array-based file systems

Abstract

Striping files across the disks of a disk array is a promising approach to improve the I/O performance of data management systems. An important tuning parameter of this method is the striping unit that is, the maximum number of logically consecutive blocks that are allocated on one disk. The striping unit determines the degree of parallelism in servicing a request by multiple disks, and its affects the achievable throughput of I/O requests. Since a good choice of a file's striping unit depends on the file's access characteristics such as average request size, it is proposed that file-specific striping units be chosen rather than choosing the same global striping unit for all files. The paper presents a method for tuning file-specific striping units, based on the access characteristics of the individual files and the throughput requirements of the application. Performance experiments are presented, based on a synthetic benchmark that was run on the file system prototype FIVE and a simulation testbed for disk-arrays. The experiments indicate significant performance gains of file-specific striping units compared to an optimally chosen global striping unit. >