IOScheduling

What is FCFS Disk Scheduling?

First-Come-First-Served (FCFS) disk scheduling services disk I/O requests in the exact order they arrive in the queue, moving the disk head to each requested c…

What is SSTF Disk Scheduling?

Shortest-Seek-Time-First (SSTF) disk scheduling always services the pending request whose cylinder is closest to the disk head’s current position, greedily min…

What is SCAN Disk Scheduling?

SCAN disk scheduling moves the disk head in one direction across the disk, servicing every pending request it passes along the way, until it reaches the far ed…

What is the C-SCAN Disk Scheduling Algorithm?

C-SCAN (Circular SCAN) services disk requests by sweeping the head in one direction only to the end of the disk, then jumping immediately back to the starting…

What is the LOOK Disk Scheduling Algorithm?

LOOK is a disk scheduling algorithm that moves the head in one direction servicing requests, but reverses as soon as there are no more requests in that directi…

What are I/O Scheduling Strategies?

I/O scheduling strategies are the algorithms an OS uses to order pending disk requests so as to minimize seek time and maximize throughput, with FCFS, SSTF, SC…

SSD Scheduling Considerations vs Hard Disks

Because SSDs have no moving read/write head, seek-minimizing algorithms like SCAN or SSTF give little benefit and can even hurt performance, so OS I/O schedule…

What Are the Process Scheduling Queues in an OS?

An operating system tracks processes through several distinct scheduling queues — the job queue, the ready queue, and one or more device (I/O) queues — and a p…