On Disk Scheduling and Data Placement for Video Servers

Magnetic disks have established themselves as the mass storage device of choice for data inten sive applications including video servers These devices are mechanical in nature They perform useful work when transfering data and wasteful work when preparing to transfer data For video servers a disk can support a higher number of simultaneous displays when its percentage of wasteful work is minimized The focus of this study is on two recently introduced techniques that minimize the wasteful work performed by a disk The rst controls the placement of data across the surface of a disk while the second employs the disk scheduling policy In addition to quantifying the tradeo s associated with these two techniques we observe that one is orthogonal to the other and combine them into one display strategy We also quantify the memory require ment of these two techniques with both a coarse grain and a ne grain memory sharing technique