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Higher density means more data moves under the head for any given mechanical movement. For example, we can calculate the effective transfer speed for a floppy disc by determining how fast the bits move under the head. A standard 3½-inch floppy disk spins at 300 rpm, and the innermost track is about 66 mm long (10.5 mm radius). At 300 rpm the ...
High density (HD) 3½-inch disks switch to a cobalt disk coating, just as with 5¼-inch HD disks. Drives use 700-oersted write heads for a density of 17,434 bpi. Extra-high density (ED) doubles the capacity over HD by using a barium ferrite coating and a special write head that allows the use of perpendicular recording. [1] [2]
In the case of a disk seen face-on, area density for a given area of the disk is defined as column density: that is, either as the mass of substance per unit area integrated along the vertical path that goes through the disk (line-of-sight), from the bottom to the top of the medium:
A hard disk head on an access arm resting on a hard disk platter. The access time or response time of a rotating drive is a measure of the time it takes before the drive can actually transfer data. The factors that control this time on a rotating drive are mostly related to the mechanical nature of the rotating disks and moving heads. It is ...
The response time is the sum of three numbers: [3] Service time - How long it takes to do the work requested. Wait time - How long the request has to wait for requests queued ahead of it before it gets to run. Transmission time – How long it takes to move the request to the computer doing the work and the response back to the requestor.
As can be estimated from weight loss and the density , the wear coefficient can also be expressed as: [2] K = 3 H W P L ρ {\displaystyle K={\frac {3HW}{PL\rho }}} As the standard method uses the total volume loss and the total sliding distance, there is a need to define the net steady-state wear coefficient:
File Allocation Table (FAT) is a file system developed for personal computers and was the default file system for the MS-DOS and Windows 9x operating systems. [citation needed] Originally developed in 1977 for use on floppy disks, it was adapted for use on hard disks and other devices.
The elevator algorithm, or SCAN, is a disk-scheduling algorithm to determine the motion of the disk's arm and head in servicing read and write requests.. This algorithm is named after the behavior of a building elevator, where the elevator continues to travel in its current direction (up or down) until empty, stopping only to let individuals off or to pick up new individuals heading in the ...