SCAN-EDF is a hybrid algorithm that combines EDF with SCAN scheduling.
SCAN-EDF starts with EDF ordering but services requests with the same deadline using SCAN order.
What if several requests have different deadlines that are relatively close together?
In this case, SCAN-EDF may batch requests, using
SCAN ordering to service requests in the same batch. There are many techniques
for batching requests with similar deadlines; the only requirement is that
reordering requests within a batch must not prevent a request from being
serviced by its deadline. If deadlines are equally distributed, batches can be
organized in groups of a certain size—say, 10 requests per batch.