Rotational Delay
Hard Drive Recovery - Rotational Delay
Rotational delay refers to the delay associated with reading or writing data on a computer’s disk drive. The term ‘rotational delay’ applies to rotating storage devices such as hard disk, floppy disks and the older drum memory devices. It refers to the time required for the specified area of the disk (or the drum) to rotate to a position where it is accessible by the read/write head.
Rotational delay can be the maximum if it needs to take a full rotation to access the relevant data. This occurs in instances when the disk has just passed the head when the request arrived.
Almost all storage devices have a constant number of revolutions per second. The maximum rotational delay is approximately equal to the reciprocal of the rotational speed. For example, if the hard disk drive has a rotational speed of 7200 revolutions per minute, the maximum rotational delay will be 60/7200 or approximately 8 minutes. Average rotational delay is often interpreted as the half of the maximum rotational delay.
Rotational delay, along with seek time and transfer time, constitutes the access time. Access time refers to the time required for a computer to process the data from the processing unit and then retrieve the required data from the storage devices.
