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A hard disk drive (HDD), commonly shortened to “hard drive,” is a nonvolatile storage device: it keeps data when power is off. It records information magnetically on rigid platters that spin inside the drive. A motor turns the platters while movable read/write heads access the data.
What does HDD mean?
HDD stands for hard disk drive. “Hard drive” is the common shortened name. Unlike volatile memory, an HDD retains its stored information when the device has no power. IBM describes a hard drive as a data-storage device used in laptops and desktop computers (IBM).
How does a hard disk drive work?
An HDD stores data as magnetic patterns on one or more rigid disks called platters. The platters rotate on a spindle, and read/write heads move across their surfaces to reach the data.
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- Spinning: A spindle motor turns the platters.
- Positioning: An actuator moves the read/write heads to the needed location.
- Writing: The head changes magnetic patterns on the platter to record information.
- Reading: The head senses magnetic fields and translates them into digital information.
The disks, spindle motor, heads, and actuator sit inside a sealed enclosure, as IBM explains in its overview of hard disk drive construction.
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How is an HDD different from an SSD?
The main difference is how each technology stores data. An HDD records it magnetically on rotating platters; a solid-state drive (SSD) stores it electronically in semiconductor memory. An HDD is electromechanical, with moving parts, while an SSD has no spinning platters or moving read/write head.
| Feature | HDD | SSD |
|---|---|---|
| Storage method | Magnetic recording on rotating platters | Electronic storage in semiconductor memory |
| Moving parts | Spinning platters and moving read/write heads | No spinning platters or moving read/write head |
Neither technology is automatically the right choice for everyone. Consider the capacity, performance, physical form factor, and workload required for your device, and compare specifications for the particular products you are considering. This explanation does not establish current prices or product-level performance figures.
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What forms do HDDs come in?
HDDs are available as internal drives installed in a computer and as external or portable drives. Before choosing one, check the device it will connect to, the required connection, the physical form factor, and what you plan to store or do with it. These details determine which drive is suitable; the term “HDD” alone does not specify them.
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