FSCAN is a

disk scheduling Input/output (I/O) scheduling is the method that computer operating systems use to decide in which order I/O operations will be submitted to storage volumes. I/O scheduling is sometimes called disk scheduling. Purpose I/O scheduling usually ...

algorithm to determine the motion of the disk's arm and head in servicing read and write requests. It uses two sub-queues. During the scan, all of the requests are in the first queue and all new requests are put into the second

queue __NOTOC__ Queue () may refer to: * Queue area, or queue, a line or area where people wait for goods or services Arts, entertainment, and media *''ACM Queue'', a computer magazine * ''The Queue'' (Sorokin novel), a 1983 novel by Russian author ...

. Thus, service of new requests is deferred until all of the old requests have been processed. When the scan ends, the arm is taken to the first queue entries and is started all over again.

Analysis

FSCAN along with N-Step-SCAN prevents "arm stickiness" unlike SSTF,

SCAN Scan may refer to: Acronyms * Schedules for Clinical Assessment in Neuropsychiatry (SCAN), a psychiatric diagnostic tool developed by WHO * Shared Check Authorization Network (SCAN), a database of bad check writers and collection agency for bad ...

, and

C-SCAN The elevator algorithm (also SCAN) is a disk- scheduling algorithm to determine the motion of the disk's arm and head in servicing read and write requests. This algorithm is named after the behavior of a building elevator, where the elevator con ...

. Arm stickiness in those other algorithms occurs when a stream of requests for the same track causes the disk arm to stop progressing at that track, preferring to satisfy the no-seek requests for the track it is on. Because FSCAN separates requests into two queues, with new requests going into a waiting queue, the arm continues its sweep to the outer track and is therefore not "sticky." There is an obvious trade-off in that the requests in the waiting queue must wait longer to be fulfilled, but in exchange FSCAN is more fair to all requests.

Variations

There can be multiple variations of this algorithm. Instead of using just 2 queues, one can use N queues (with N greater than 2). The benefit of using N queues is there would be limited number of entries in a given queue and hence the reference string queue would take lesser time to get completed. Hence, the queues will get swiped faster which in turn improves the responding time of algorithm (refer to

See Also See also may refer to: * Citation signal, reference formats which often appear in technical, scientific, and legal documents * cf., an abbreviation for confer, meaning "compare" or "consult" * viz. {{disambig ...

section).