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Arbiter for mass storage access in an operating system
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
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I/O scheduling usually has to work with
hard disk drives
that have long
access times
for requests placed far away from the current position of the
disk head
(this operation is called a
seek
). To minimize the effect this has on system performance, most I/O schedulers implement a variant of the
elevator algorithm
that reorders the incoming randomly ordered requests so the associated data would be accessed with minimal head movement.
I/O schedulers can have many purposes depending on the goals; common purposes include the following
- To minimize time wasted by hard disk seeks
- To prioritize a certain
processes
' I/O requests
- To give a share of the disk bandwidth to each running process
- To guarantee that certain requests will be issued before a particular deadline
Disciplines
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Common scheduling disciplines include the following:
See also
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References
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Further reading
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External links
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