N-Step-SCAN

N-Step-SCAN (also referred to as N-Step LOOK) is a disk scheduling algorithm to determine the motion of the disk's arm and head in servicing read and write requests. It segments the request queue into subqueues of length N. Breaking the queue into segments of N requests makes service guarantees possible. Subsequent requests entering the request queue won't get pushed into N sized subqueues which are already full by the elevator algorithm. As such, starvation is eliminated and guarantees of service within N requests is possible.

Analysis

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

See also

Other variations include:

• SCAN - Elevator Algorithm
• FSCAN
• LOOK (and C-LOOK)

References