It is made up of one or more sectors. Track — A track is one complete circle of data on one side of a hard drive platter. A track is broken into groups of sectors. Cylinder — A cylinder is a stack of tracks lined up one on top of another to form a cylinder shape. Drive mapping — Drive mapping is a letter assigned to a physical or logical drive.
A track is that portion of a disk which passes under a single stationary head during a disk rotation, a ring 1 bit wide. Each cylinder is equidistant from the center of the disk.
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Follow What are Hard Disk sector , block , cluster , track , cylinder and head? Upvote 2 Views Followers 8. Write an Answer Register now or log in to answer. Cylinders are the system of identical tracks on multiple platters within the drive. The multiple arms of a drive move together in lockstep, positioning the heads in the same relative location on all platters simultaneously.
Disk Partitions Disk partitions divide the capacity of physical disk drives into logical containers. A disk drive can have one or more partitions, providing a way for users to flexibly create different virtual disks that can be used for different purposes. For instance, a system could have different partitions to reserve storage capacity for different users of the system or for different applications.
A common reason for using multiple partitions is to store data for operating systems or file systems. Machines that are capable of running two different operating systems, such as Linux and Windows, could have their respective data on different disk partitions. Disk partitions are created as a contiguous collection of tracks and cylinders. Visually, you can imagine partitions looking like the concentric rings of an archery target with the bull's eye being replaced by the disk motor's spindle.
Partitions are established starting at the outer edge of the platters and working toward the center. For instance, if a disk has three partitions, numbered 0, 1, and 2, partition 0 would be on the outside and partition 2 would be closest to the center. Logical Block Addressing While the internal system of cylinders, tracks, and sectors is interesting, it is also not used much anymore by the systems and subsystems that use disk drives.
Cylinder, track, and sector addresses have been replaced by a method called logical block addressing LBA , which makes disks much easier to work with by presenting a single flat address space. To a large degree, logical block addressing facilitates the flexibility of storage networks by allowing many different types of disk drives to be integrated more easily in a large heterogeneous storage environment.
With logical block addressing, the disk drive controller maintains the complete mapping of the location of all tracks, sectors, and blocks in the disk drive. There is no way for an external entity like an operating system or subsystem controller to know which sector its data is being placed in by the disk drive. At first glance this might seem risky letting a tiny chip in a disk drive be responsible for such an important function. But, in fact, it increases reliability by allowing the disk drive to remap sectors that have failed or might be headed in that direction.
Considering the areal density and the microscopic nature of disk recording, there are always going to be bad sectors on any disk drive manufactured. Disk manufacturers compensate for this by reserving spare sectors for remapping other sectors that go bad. Because manufacturers anticipate the need for spare sectors, the physical capacity of a disk drive always exceeds the logical, usable capacity.
Reserving spare sectors for remapping bad sectors is an important, reliability-boosting by-product of LBA technology.
Disk drives can be manufactured with spare sectors placed throughout the platter's surface that minimize the performance hit of seeking to remapped sectors. Geometry of Disk Drives and Zoned-Bit Recording There is no way to escape radial geometry when working with disk drives. One of the more interesting aspects of this radial geometry is that the amount of recording material in a track increases as you move away from the center of the disk platter. Disk drive tracks can be thought of as media rings having a circumference that is determined by the mathematical expression 2pr, where r is the radius for the track.
The amount of recording material in a track is determined by radial length. This means that the outermost tracks can hold more data than the inside tracks. In fact, they can hold a lot more data than inside tracks. To take advantage of this geometry, disk drive designers developed zoned-bit recording, which places more sectors inside tracks as the radius increases. The outermost zone, zone 0, has the most sectors per track, while the innermost zone has the fewest.
As platters are never exchanged between disk drives, there is no need to worry about standardized zone configurations. The tracks, stacked on top of each other form a cylinder. This scheme is slowly being eliminated with modern hard drives. 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. 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.
Tracks are numbered, starting at 0 the outermost edge of the disk , and going up to the highest numbered track, typically , close to the center. Similarly, there are 1, cylinders numbered from 0 to on a hard disk. The stack of platters rotate at a constant speed. 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.
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 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. The disk space is filled with data according to a standard plan. One side of one platter contains space reserved for hardware track-positioning information and is not available to the operating system.
Thus, a disk assembly containing two platters has three sides available for data. Track-positioning data is written to the disk during assembly at the factory. The system disk controller reads this data to place the drive heads in the correct sector position. A sector, being the smallest physical storage unit on the disk, is almost always bytes in size because is a power of 2 2 to the power of 9. The number 2 is used because there are two states in the most basic of computer languages — on and off.
Each disk sector is labelled using the factory track-positioning data. Sector identification data is written to the area immediately before the contents of the sector and identifies the starting address of the sector.
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