Magnetic Hard Drive Geometry

• Overview of traditional mechanical hard drives

• Focuses on components and structure for data storage

Platters

• Material: Glass/Aluminum with magnetic coating

• Number: One or more platters contribute to total storage

• Surfaces: Data is stored on both sides of the platters

Tracks

• Definition: Concentric circles on platter surfaces

• Numbering: Numbered from the outer edge inward

• Measurement: Measured in tracks per inch (TPI)

Sectors

• Definition: Sections within tracks

• Size: Traditionally 512 bytes each (modern drives: 4 KB)

• Contents: Includes data, preamble, and ECC (Error Correction Code)

Cylinders

• Definition: Vertical alignment of tracks across platters

• Function: Allows multi-platter data reading/writing

• Benefit: Simplifies data access by aligning tracks

Read/Write Heads

• Operation: Float above platters for non-contact operation

• Technology: Use electromagnetism for data interaction

• Positioning: Positioned by actuator arm over tracks

Actuator Arm and Motor

• Function: Positions read/write heads precisely using voice coil motor

• Benefit: Allows fast, smooth head movement

Spindle Motor

• Role: Rotates platters at consistent speeds (e.g., 5,400 RPM, 7,200 RPM)

• Impact of RPMs: Higher RPMs lead to faster data read/write speeds

Magnetic Coating

• Composition: Thin film of iron oxide or cobalt-based alloy

• Function: Changes polarity to represent 1s and 0s

• Engineering Goal: Designed for stability and longevity

Servo Information

• Purpose: Guides head positioning and track alignment

• Mechanism: Uses embedded servo sectors for positioning data

Logical Structure

• Method: Uses Logical Block Addressing (LBA) for simplified access

• Concept: Treats drive as a continuous sequence of addressable blocks

Error Detection

• Technology: Utilizes ECC to detect/correct minor read errors

• Goal: Enhances data reliability through error correction codes