Data Organization and Formatting

• Concentric rings or tracks

—   Gaps between tracks

—   Reduce gap to increase capacity

—   Same number of bits per track (variable packing density)

—   Constant angular velocity

• Tracks divided into sectors


• Minimum block size is one sector


• May have more than one sector per block

Disk Data Layout

Characteristics

• Fixed (rare) or movable head


• Removable or fixed


• Single or double (usually) sided


• Single or multiple platter


• Head mechanism

—   Contact (Floppy)

—   Fixed gap

—   Flying (Winchester)

Fixed/Movable Head Disk

• Fixed head

—   One read write head per track

—   Heads mounted on fixed ridged arm

• Movable head

—   One read write head per side

—   Mounted on a movable arm

Removable or Not

• Removable disk

—   Can be removed from drive and replaced with another disk

—   Provides unlimited storage capacity

—   Easy data transfer between systems

• Nonremovable disk

—   Permanently mounted in the drive

Multiple Platter

• One head per side


• Heads are joined and aligned


• Aligned tracks on each platter form cylinders


• Data is striped by cylinder

—   reduces head movement

—   Increases speed (transfer rate)

Multiple Platters

Cylinders