Group-Sweeping Scheduling

Group-Sweeping Scheduling

(storage, algorithm)(GSS) A disk scheduling strategy in whichrequests are served in cycles, in a round-robin manner. Toreduce disk arm movements ("seeking"), the set of streams isdivided into groups that are served in fixed order. Streamswithin a group are served according to "SCAN".

If all clients are assigned to one group, GSS reduces to SCAN,and if all clients are assigned to separate groups, GSSeffectively becomes round-robin scheduling. The service orderwithin one group is not fixed, and a stream may in fact befirst in one cycle while last in the next. This variation hasto be masked by extra buffering but whereas SCAN requiresbuffer space for all streams, GSS can reuse the buffer foreach group and effect a trade-off between seek optimisationand buffer requirements.