Performance analysis of RAIDS disk arrays with a vacationing servermodel for rebuild mode operation

摘要

We analyze the performance of RAIDS disk arrays in normal,ndegraded, and rebuild modes. The analysis, which is shown to be highlynaccurate through validation against simulation results, achieves itsnaccuracy by (1) modeling detailed disk characteristics; (2) developing ansimple approximation to compute the mean response time for fork-joinnrequests arising in degraded mode operation; and (3) using a vacationingnserver model with multiple vacation types for rebuild mode analysis.nAccording to this model vacations (rebuild reads) are started when thenserver (disk) becomes idle and are repeated until the arrival of annexternal disk request. Type one (two) vacations correspond to thenreading of the first track which requires a seek (successive tracksnrequiring no seeks). The analytic solution is used to quantify theneffect of different rebuild options, such as read redirection and thensplit-seek option