# hard disk

> data storage device

**Wikidata**: [Q4439](https://www.wikidata.org/wiki/Q4439)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Hard_disk_drive)  
**Source**: https://4ort.xyz/entity/hard-disk

## Summary
A **hard disk** (or **hard disk drive, HDD**) is a magnetic data storage device used in computers to store and retrieve digital information. It consists of rotating platters coated with magnetic material and read/write heads that access data, serving as a primary form of non-volatile storage in computing systems.

## Key Facts
- **Invented in 1956**, the hard disk was the first high-capacity, non-volatile storage solution for computers.
- Uses **magnetic storage** to record data on spinning platters, typically made of aluminum or glass.
- Classified as **computer hardware** and a type of **disk drive**, distinct from solid-state drives (SSDs).
- Key components include **platters, spindle, read/write heads, housing, and interfaces** (e.g., SATA).
- Notable models include the **ST-506 (1980)**, **HP Kittyhawk (1992)**, and **Seagate Barracuda series**.
- Available in form factors like **3.5-inch (desktop) and 2.5-inch (laptop)**.
- Preceded by **solid-state drives (SSDs)**, which offer faster speeds but were historically more expensive.

## FAQs
### Q: What is the difference between a hard disk and an SSD?
A: A hard disk uses spinning magnetic platters to store data, while an SSD relies on flash memory with no moving parts. SSDs are faster and more durable but were traditionally costlier per gigabyte.

### Q: When was the first hard disk invented?
A: The hard disk was introduced in **1956** as the first high-capacity, non-volatile storage device for computers.

### Q: What are the main components of a hard disk?
A: Core components include **magnetic platters, a spindle motor, read/write heads, an actuator arm, and a controller board**.

### Q: Are hard disks still used today?
A: Yes, hard disks remain widely used for **bulk storage** due to their lower cost per gigabyte, though SSDs dominate in performance-critical applications.

### Q: What is a "platter" in a hard disk?
A: A platter is a **circular disk coated with magnetic material** where data is stored. Multiple platters increase storage capacity.

## Why It Matters
The hard disk revolutionized computing by providing **reliable, high-capacity storage** that persisted without power. Before SSDs, it was the dominant medium for operating systems, applications, and user data. Its invention enabled the development of modern personal computers, servers, and data centers. While SSDs have surpassed HDDs in speed and durability, hard disks remain essential for **cost-effective storage**, archival purposes, and legacy systems. Their impact extends beyond computing into consumer electronics (e.g., DVRs, gaming consoles) and enterprise infrastructure, shaping how data is managed globally.

## Notable For
- **First non-volatile storage solution** for computers, replacing slower and less reliable methods like punch cards and magnetic tape.
- **High storage capacity at low cost**, making it the standard for decades before SSD adoption.
- **Mechanical precision engineering**, with components like flying heads hovering nanometers above platters.
- **Longevity in the market**, with models like the **Seagate Barracuda** and **Western Digital Black** becoming industry staples.
- **Adaptability**, evolving from **5.25-inch drives (1980s)** to compact **2.5-inch and 1.8-inch form factors**.

## Body
### **History and Evolution**
- The first hard disk, **IBM 350**, debuted in **1956** with a capacity of **5 MB** and a size comparable to a refrigerator.
- Early models like the **ST-506 (1980)** standardized the **5.25-inch form factor**, while the **ST-412 (1981)** improved reliability.
- The **1990s** saw the rise of **3.5-inch drives** (e.g., **Seagate Medalist, 1992**) and the **HP Kittyhawk**, the first **1.3-inch microdrive**.
- **SATA interfaces** (introduced in 2003) replaced older IDE/PATA connections, improving data transfer speeds.

### **Technical Specifications**
- **Platters**: Typically made of **aluminum or glass**, coated with a magnetic layer. Modern drives use **perpendicular recording** for higher density.
- **Spindle Speed**: Common speeds include **5,400 RPM (laptops)** and **7,200 RPM (desktops/servers)**; enterprise drives may reach **10,000–15,000 RPM**.
- **Capacity**: Ranges from **hundreds of gigabytes to 20+ TB** (e.g., **Seagate Exos X20**).
- **Interfaces**: **SATA, SAS, or legacy IDE/SCSI** for connectivity.
- **Cache**: Embedded **disk buffer (e.g., 64 MB–256 MB)** to improve performance.

### **Types and Variants**
- **Internal HDDs**: Fixed inside computers (e.g., **WD Black, Seagate Barracuda**).
- **External HDDs**: Portable or desktop models with USB/eSATA connections.
- **Removable HDDs**: Historical designs (e.g., **Iomega REV**) allowing platter swaps.
- **Hybrid Drives (SSHDs)**: Combine HDD capacity with a small SSD cache for performance boosts.

### **Decline and Legacy**
- **SSDs** began replacing HDDs in the **2010s** due to superior speed, durability, and power efficiency.
- HDDs remain dominant in **data centers, NAS systems, and budget builds** where cost-per-TB is critical.
- **Archival use**: HDDs are preferred for **cold storage** due to lower cost and higher capacities (e.g., **20 TB Seagate Exos X20**).

## Schema Markup
```json
{
  "@context": "https://schema.org",
  "@type": "Thing",
  "name": "hard disk",
  "description": "A magnetic data storage device used in computers to store and retrieve digital information.",
  "url": "https://en.wikipedia.org/wiki/Hard_disk_drive",
  "sameAs": [
    "https://www.wikidata.org/wiki/Q4837690",
    "https://en.wikipedia.org/wiki/Hard_disk_drive"
  ],
  "additionalType": [
    "https://www.wikidata.org/wiki/Q188915",  // computer hardware
    "https://www.wikidata.org/wiki/Q1139629"   // computer storage media
  ]
}

## References

1. [Source](https://github.com/JohnMarkOckerbloom/ftl/blob/master/data/wikimap)
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3. [Source](https://www.compart.com/en/unicode/U+1F5B4)
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7. Freebase Data Dumps. 2013
8. MusicBrainz
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12. [Source](https://thenextweb.com/vocabulary/hard-disk-drive/)
13. National Library of Israel
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