Disk Arrays or RAIDs are a widely accepted I/O system architecture, useful for a wide range of applications. Before a RAID can be used, one needs to configure the RAID to select parameters such as the RAID level to use, the stripe unit to use, how large of a cache to use, and so on. Selecting these configuration parameters can be quite complex, yet no aids are available today to help the user configure his RAID. The optimal selection of the parameters strongly depends on the specific workload characteristics of the application. In this paper, we describe a configuration tool called Raidtool which is intended to support the systems designer in the selection of the configuration parameters. Our approach consists of three basic steps. The first step is to collect a trace of I/Os while running one or more typical applications. In the second step, this trace data is analyzed to determine the workload characteristics of the applications. In the third and final step, we use a simulator to evaluate the different RAID controller configurations.
