Optimum Head Separation in a Disk System with Two Read/Write Heads
Journal of the ACM (JACM)
Queueing models of secondary storage devices
Queueing Systems: Theory and Applications
Computer Storage Systems and Technology
Computer Storage Systems and Technology
Why specialized disks for composite operations may be unnecessary
ACM SIGARCH Computer Architecture News
| Hi-index | 14.98 |
The authors analyze a model of a movable-head disk system with two read/write heads maintained a fixed distance d apart on each arm. Successive request-addresses are assumed to be independent random variables, uniformly distributed over the set of cylinders. The purpose of the analysis is to find that value of d which minimizes the expected seek time per request, assuming that seek time varies linearly with the distance z traveled by the heads. The authors extend an earlier analysis of this model to more general seek-time characteristics which take into account nonlinear acceleration effects. Detailed results, combining both analysis and simulation experiments, are presented for seek times linear in z/sup alpha /, 0or= alpha or=1. An unexpected result of the study was that the value of d which minimizes expected seek time is very nearly independent of alpha.