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Cylinder, head, and sector of a hard drive. Cylinder-head-sector (CHS) is an early method for giving addresses to each physical block of data on a hard disk drive. It is a 3D-coordinate system made out of a vertical coordinate head, a horizontal (or radial) coordinate cylinder, and an angular coordinate sector. Head selects a circular surface ...
In logical block addressing, only one number is used to address data, and each linear base address describes a single block. The LBA scheme replaces earlier schemes which exposed the physical details of the storage device to the software of the operating system. Chief among these was the cylinder-head-sector (CHS) scheme, where blocks were addressed by means
A right circular hollow cylinder (or cylindrical shell) is a three-dimensional region bounded by two right circular cylinders having the same axis and two parallel annular bases perpendicular to the cylinders' common axis, as in the diagram. Let the height be h, internal radius r, and external radius R.
Within the disk drive, this linear block number was translated into a cylinder number, head number and sector number. Moving the translation into the disk drive allowed drive manufacturers to place a different number of blocks on each track transparently to the accessing software.
Likewise, for drives that have a pseudo-geometry of 255 heads per cylinder (which may be determined by your operating system these days; e.g., many Linux installs are based on only 16 heads/cylinder, whereas the same physical disk might have 255 heads/cylinder under a Windows OS), the following would be true:
A cylinder is a basic curvilinear geometric shape. Cylinder may also refer to: Cylinder (algebra), the Cartesian product of a set with its superset; Cylinder (disk drive), a division of data in a disk drive; Cylinder (engine), the space in which a piston travels in an engine; Cylinder (firearms), the rotating part of a revolver containing ...
Physical records can have any size up to the limit of a track, but some devices have a track overflow feature that allows breaking a large block into track-size segments within the same cylinder. The queued access methods, such as QSAM, are responsible for blocking and deblocking logical records as they are written to or read from external media.
Cylinder partition alignment, partitions starting on logical or physical cylinder boundaries on hard disk drives SSD partition alignment , partitions starting on NVM boundaries (with typically 4 KB to 1 MB in LBAs size) on SSDs and other flash-based memory devices