Hard Disk Drive (HDD)
A Hard Disk Drive (HDD) is a non-volatile data storage device that stores and retrieves digital information using magnetic storage. It consists of one or more rapidly rotating disks (platters) coated with magnetic material, along with read/write heads that move over the disk surfaces to access or modify data.
Key Components of an HDD
- Platters – Circular disks coated with magnetic material where data is stored.
- Spindle Motor – Rotates the platters at high speeds (typically 5,400 RPM to 7,200 RPM, or up to 15,000 RPM for enterprise drives).
- Read/Write Heads – Tiny electromagnetic devices that read and write data on the platters.
- Actuator Arm – Moves the read/write heads across the platters.
- Controller Board – The circuit board that manages data transfer between the HDD and the computer.
- Cache (Buffer Memory) – A small amount of high-speed memory (e.g., 32MB to 256MB) that temporarily stores frequently accessed data.
How It Works:
- It contains one or more spinning disks (called platters) coated with magnetic material.
- A read/write head moves over the surface of these disks to read or write data.
- The data is stored magnetically, so it’s non-volatile – meaning it stays even when the power is off.
Types of Hard Disk Drives (HDDs):
1. Internal HDD
- Installed inside a computer/laptop.
- Connects via SATA (Serial ATA) or older PATA (Parallel ATA/IDE) interfaces.
- Common sizes: 3.5-inch (desktops) and 2.5-inch (laptops).
2. External HDD
- Portable storage connected via USB, Thunderbolt, or eSATA.
- Used for backups, extra storage, and data transfer.
3. Enterprise HDD
- Designed for servers and data centers.
- Higher reliability, faster speeds (10,000 RPM or 15,000 RPM), and larger capacities.
- Examples: Western Digital Gold, Seagate Exos.
4. NAS HDD (Network-Attached Storage HDD)
- Optimized for 24/7 operation in NAS systems.
- Better durability and vibration resistance.
- Examples: WD Red, Seagate IronWolf.
5. Surveillance HDD
- Designed for continuous writing in security camera systems.
- Handles high workloads and long recording sessions.
- Examples: WD Purple, Seagate SkyHawk.