There’re three types of data storage devices: Electrical, Optical and Magnetic data storage devices.

Electrical data storage devices : USB, CF card, SD card, Memory Stick , SSD etc;
Optical data storage devices: CD, VCD, DVD, blue ray, etc;
Magnetic data storage devices: Tape, Hard Disk Drive etc.

Hard disk drive overview

History: IBM’s RAMAC is introduced in 1956. It has 5MB with 50 24 inch disks.
Form Factors: 1.8 inch, 2.5 inch, 3.5 inch etc
Speed: 4200 rpm, 5400 rpm, 7200 rpm etc
Capacity: 2TB is maximum
Interface: IDE, SATA PCMICA, SCSI etc

HDD Physical Structure

HDD physical structure contains mainly three parts: Magnetic, Mechanical and Electrical parts.
Hard drive physical structure overview

Top Cover: Functionality: Seal the drive case and with informative label; Label: information about the drive, including Model, Serial Number, LBA, Date etc. Used for donor criteria;

HDD Platter: Functionality: Functionality: storing the data, made up of aluminium or glass; Platter Size: disk diameter, also called as form factor. 5.25 inch, 3.5 inch, 2.5 inch etc; Platter Number: One or multiple platters; Magnetic Media: a very thin coating of magnetic materials; Oxide Media and Thin Film Media; Protective Layer: On top of magnetic media layer, super-thin, protective, lubricating layer of materials; Platter scratch: one of the most common hdd physical damage and not easy to recover the lost data in this situation; on the platters, there’re tracks: concentric circles on platter and sectors: units in a track; Data Area: User Data storage area; Service Area: Service Data (Firmware) storage area, outer of disk track.

Spindle Motor: It’s to rotate the HDD platters; Spindle Speed: 4200 rpm, 5400 rpm, 7200 rpm, 10,000 rpm etc
Spindle Motor Overview

Heads Assembly: Read/Write Head, Slider, Arm Actuator;

Read/Write Heads: data read/recording by transform between electrical signals to magnetic signals.
Number of Heads:
Flying Height: distance between head and platter.
Head Crashes: accidental contact of head and disk platter
Heads Type: Thin Film, MR, GMR etc
Heads Slider: Each hard disk head is therefore mounted to a special device called a head slider or just slider for short;
Heads Arm: onto which sliders are mounted, metal, triangular in shape;
Heads Actuator: control movement of heads arm;
Servo System: closed—loop feedback system
Servo Code and Servowriter
Landing Zone; Head Park;

PCB: Printed Circuit Board
MPU: controller chip
VCM&Spindle Motor
Read/Write Channel Chip
Preamplifier Chip
RAM/Cache
ROM
Connectors

Hard disk drive physical damages:
PCB Damage: burnt, ROM code corruption
Head Assembly Damage: heads damage, disk scratch, motor get stuck;

Symptom of PCB damage: motor no spin up
Solution: PCB repair or replacement
Donor Criteria
Hot Swap

Symptom of Head Assembly damage: motor no spin up
Solution: head replacement or platter swap
Donor criteria

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