You can call them hard disks, physical disks, fixed disks or hard drives but they are all the same thing: a device used to store information. Hard Disks are used to store information, but they hold so much information that a system of organizing the storage space is needed in order to quicly find and retreive information stored on the disk.
Disk Components
Disk drives are composed of multiple components that all go together to make a physical disk function.
- Platters
- Spindle
- Read-Write Head
- Head sliders
- Arms
- Actuators
- Drive Electronics
- Jumpers
- Logic
- Cache
Platters are disks of metal coated in magnetically-sensitive metal oxids that are used to store information. The platters are attached to a spindle and are stacked on top of each other.
The spindle is the axle that runs through the center of the platters. The spindle is used to rotate the platters at speeds of 4,500, 7,200 and 10,000 rotations per minute (RPM). This rotation speed is often called the spindle speed of the disk.
The read-write head reads and writes data to the platters as it floats above the platter on a cushion of air created by the spindle rotating the platters at high speed. The read-write head can move back and forth across the surface of the platter as it seeks informtation or writes data to the platters. In most modern disk drives, there are multiple read-write heads on each platter.
Disk Geometry
- Blocks
- Tracks
- Sectors
- Cylinders