The data are typically stored on disk by following a well-defined physical allocation scheme whereby you can reach the area where you can read / write data to disk. One of the most common is called CHS acronym for the English word Cylinder / Head / Sector (Cylinder / Head / Sector), in this structure the data is stored as a physical address having a number for each of the following physical entities:
structure of the surface of a plate
A) Track
B) Sector
C) Sector of a track
D) Cluster, along of contiguous sectors
- Plate
- a hard disk consists of one or more disks in parallel, with each area, called "flat" and identified by a unique number, is for storing data.
- Track
- each plate consists of several concentric rings numbered, called tracks, each identified by a unique number.
- cylinder
- the set of tracks at the same distance from the center on all the discs is said cylinder. Match All tracks with the same number but different dish.
- Industry
- each plate is divided into circular sectors, or in slices in the same radial each identified by a unique number.
- Block
- The set of sectors in the same location in all dishes.
- head
- On each plate is a head to read or write access to data stored on the plate, the position of that head is solidarity with all the other dishes on the other. In other words, if a head is positioned over a track, all the heads are positioned in the cylinder to which the track belongs.
This structure introduces a physical disk geometry that consists of a series of "coordinate" CHS, indicating expressible cylinder, head, sector. In this way you can uniquely address each block of data on the disk. For example, if a hard disk consists of two disks (or equivalently 4 plates), 16384 cylinders (or equivalently 16,384 tracks per plate) and 16 sectors of 4096 bytes per track, then the disk capacity is 4 × 16 × 16384 × 4096 bytes, or 4 GiB.
The interleaving factor is the number of sectors of the hard disk that you must jump to read sequentially all of the track. This depends largely on the performance characteristics of the hard disk itself, ie the speed of rotation of the disc, by the movement of seekers with their heads, and the speed of read-write head of the same.
This process was initially introduced as the CPU, receiving and reworking of the data read, do these things at a slower rate of speed read / write to your hard drive, and then, once revised data from a field The head are already past the beginning of the next sector. Alternating areas on a regular basis and reading according to the specific interleaving factor, speeds up disk rigido e il calcolatore. I moderni dischi rigidi non necessitano di interleaving.
