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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 .
The scheduler is an operating system module that selects the next jobs to be admitted into the system and the next process to run. Operating systems may feature up to three distinct scheduler types: a long-term scheduler (also known as an admission scheduler or high-level scheduler), a mid-term or medium-term scheduler, and a short-term scheduler.
However, since the buffer is always getting new requests, these can skew the service time of requests that may be farthest away from the disk head's current location, if the new requests are all close to the current location; in fact, starvation may result, with the faraway requests never being able to make progress.
When the operating system creates a new process, that process is initially labeled as NOT RUNNING, and is placed into a queue in the system in the NOT RUNNING state. The process (or some portion of it) then exists in main memory , and it waits in the queue for an opportunity to be executed.
Anticipatory scheduling overcomes deceptive idleness by pausing for a short time (a few milliseconds) after a read operation in anticipation of another close-by read requests. [2] Anticipatory scheduling yields significant improvements in disk utilization for some workloads. [3]
Shortest remaining time, also known as shortest remaining time first (SRTF), is a scheduling method that is a preemptive version of shortest job next scheduling. In this scheduling algorithm, the process with the smallest amount of time remaining until completion is selected to execute. Since the currently executing process is the one with the ...
NCQ can negatively interfere with the operating system's I/O scheduler, decreasing performance; [8] this has been observed in practice on Linux with RAID-5. [9] There is no mechanism in NCQ for the host to specify any sort of deadlines for an I/O, like how many times a request can be ignored in favor of others.
Device Manager is a component of the Microsoft Windows operating system. It allows users to view and control the hardware attached to the computer. When a piece of hardware is not working, the offending hardware is highlighted for the user to deal with.