Definition
Hard Disk Organization
A mechanical hard disk organizes data physically across rotating platters using a movable arm with read/write heads.
Physical Structure
- Platters: Circular disks coated with magnetic material. Data is stored on both sides.
- Tracks (Spuren): Concentric circles on a platter side where data is recorded.
- Sectors (Sektoren): Each track is divided into fixed-size segments called sectors, typically 512 bytes or 4KB. This is the smallest physical unit of transfer.
- Cylinders (Zylinder): The set of all tracks at the same distance from the center across all platter surfaces. Moving the arm to a specific cylinder allows access to multiple tracks without further movement.
Addressing
Data is typically addressed using:
- CHS (Cylinder-Head-Sector): A historical addressing scheme.
- LBA (Logical Block Addressing): A modern scheme where sectors are addressed as a linear sequence of blocks (). The disk controller maps LBA to the physical CHS coordinates.