Homework - 10 Version 0 |
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👤 Author: by 244045932qqcom 2019-12-18 08:22:03 |
Review various Disk scheduling algorithms
FCFS Scheduling:
First-come, first-served algorithm is just performing I/O request in the order of request arrival. This often does not provide fastest service.
SSTF Scheduling:
Shortest-seek-time-first algorithm chooses the pending request closest to the current head postion. This algorithm gives a substantial improvement in performance, but it is possible to cause starvation in some situation.
SCAN Scheduling:
In SCAN algorithm, the disk arem starts at one end of the disk and move towards the other end, servicing requests as it reached each cylinder, until it gets to the other end. Then the direction of head movement is reversed, and servicing continues.
C-SCAN Scheduling:
Circular SCAN algorithm has only one difference with SCAN. C-SCAN treats cylinder as a circular list. As head moves to one end of the disk, it moves to the other end immediately without servicnig any requests.
Look and C-Look Scheduling:
These algorithms behave just like SCAN and C-SCAN, expect their arms only go as far the final request in each direction before they change direction.