Stoage Management /
StoraSt
Disk Scheduling
Dr Nishant Jain, MITS-DU Gwalior
,Overview
A Process makes the I/O requests to the operating system to access
the disk. Disk Scheduling Algorithm manages those requests and
decides the order of the disk access given to the requests.
Disk scheduling is a technique used by the operating system to
schedule multiple requests for accessing the disk.
Dr Nishant Jain, MITS-DU Gwalior
,Why Disk Scheduling is needed?
➢ Disk Scheduling Algorithms are needed because a process can make multiple
I/O requests and multiple processes run at the same time.
➢ The requests made by a process may be located at different sectors on
different tracks. Due to this, the seek time may increase more.
➢ These algorithms help in minimizing the seek time by ordering the requests
made by the processes.
Dr Nishant Jain, MITS-DU Gwalior
, Important Terms
▪ Seek Time - It is the time taken by the disk arm to locate the desired
track.
▪ Rotational Latency - The time taken by a desired sector of the disk to
rotate itself to the position where it can access the Read/Write heads is
called Rotational Latency.
▪ Transfer Time - It is the time taken to transfer the data requested by
the processes (disk to CPU).
▪ Disk Access Time - Disk Access time is the sum of the Seek Time,
Rotational Latency, and Transfer Time.
Dr Nishant Jain, MITS-DU Gwalior
StoraSt
Disk Scheduling
Dr Nishant Jain, MITS-DU Gwalior
,Overview
A Process makes the I/O requests to the operating system to access
the disk. Disk Scheduling Algorithm manages those requests and
decides the order of the disk access given to the requests.
Disk scheduling is a technique used by the operating system to
schedule multiple requests for accessing the disk.
Dr Nishant Jain, MITS-DU Gwalior
,Why Disk Scheduling is needed?
➢ Disk Scheduling Algorithms are needed because a process can make multiple
I/O requests and multiple processes run at the same time.
➢ The requests made by a process may be located at different sectors on
different tracks. Due to this, the seek time may increase more.
➢ These algorithms help in minimizing the seek time by ordering the requests
made by the processes.
Dr Nishant Jain, MITS-DU Gwalior
, Important Terms
▪ Seek Time - It is the time taken by the disk arm to locate the desired
track.
▪ Rotational Latency - The time taken by a desired sector of the disk to
rotate itself to the position where it can access the Read/Write heads is
called Rotational Latency.
▪ Transfer Time - It is the time taken to transfer the data requested by
the processes (disk to CPU).
▪ Disk Access Time - Disk Access time is the sum of the Seek Time,
Rotational Latency, and Transfer Time.
Dr Nishant Jain, MITS-DU Gwalior
