Magnetic Storage

Tape drive

Stores data on magnetic tapes. high capacity. cost-effective. slow. mainly used for data backups nowadays. Aka. DAT drives.

Hard disk drive

Magnetic storage. Operationally identical to a conventional radio cassette tape. Uses a disk coated with magnetic medium. High data transfer speed.

Hard disk - internal structure

Capacity can be improved by adding more platters. Platters are kept in dust free environment to avoid damages because of high speed. Each side of the platter require a read/write head.

Categorized by their capacity, controller, and platter rotation speed. Capacity ranges from 500GB to 8TB. Platter rotation speeds are 3600, 5400 and 7200 RPM.

Available disk controllers:

Integrated Device Electronics
Small Computer System Interface
Serial AT Attachment Interface

Track

Single ring of data on one side of a platter.

Sector

Fixed size (usually 512 bytes) divisions (usually about 900) of a track.

Cylinder

Set of tracks on a disk, that are on each side of all platters in a stack and are at the same distance from the center of the disk.

Floppy disk drive

Removable. Has a flexible, magnetic medium that is enclosed in a (semi-)rigid plastic case.

Parts of Floppy Disk

Functionality of Floppy Disk

Paper rings are used for protection.

Flap - a small opening for the read/write head to access the disk

The head actuator mechanism is slightly different to the mechanism in a hard disk. In a hard disk the head arm moves laterally from centre of the disk towards to the edge while in a floppy disk the movement is horizontal.

The read/write head is mounted on a spindle and the spindle is controlled by a stepper motor. The high density hole is only available in High Density floppy disks.