disk formatting why are cluster sizes important

Thus, a disk assembly containing two platters has three sides available for data. One side of one platter contains space reserved for hardware track-positioning information and is not available to the operating system. The disk space is filled with data according to a standard plan. The result of the different data density is that the same amount of data can be read over the same period of time, from any drive head position. To compensate for this physical difference, tracks near the outside of the disk are less-densely populated with data than the tracks near the center of the disk. The drive head, while positioned close to the center of the disk reads from a surface that is passing by more slowly than the surface at the outer edges of the disk. The stack of platters rotate at a constant speed. Similarly, there are 1,024 cylinders (numbered from 0 to 1023) on a hard disk.

Tracks are numbered, starting at 0 (the outermost edge of the disk), and going up to the highest numbered track, typically 1023, (close to the center). To the operating system of a computer, tracks are logical rather than physical in structure, and are established when the disk is low-level formatted. All new disks use a translation factor to make their actual hardware layout appear continuous, as this is the way that operating systems from Windows 95 onward like to work. This scheme is slowly being eliminated with modern hard drives. The tracks, stacked on top of each other form a cylinder. A cylinder is formed while all drive heads are in the same position on the disk. prior to Windows 95) will refer to a cylinder/ head/ sector notation. The figure below shows a hard disk with two platters. A sector is the smallest physical storage unit on a disk, and is almost always 512 bytes (0.5 kB) in size. Sections within each track are called sectors. There can be more than a thousand tracks on a 3.5-inch hard disk.

A drive head, while in one position can read or write a circular ring, or band called a track. On a hard disk, data is stored in thin, concentric bands. In this way, the drive heads can reach the entire surface of each platter. As the platters spin, the drive heads move in toward the center surface and out toward the edge. In this description, the hard drive is mounted horizontally.Įlectromagnetic read/write heads are positioned above and below each platter. Hard disks may be mounted in a horizontal or a vertical position. A hard disk is a sealed unit containing a number of platters in a stack.

Disk formatting why are cluster sizes important