Harddisk

Hard disk, or hard disk drive (HDD), is a non-volatile storage device that records data magnetically on rotating rigid platters. Data is stored on a stack of platters with read/write heads mounted on an actuator; information is organized into tracks, sectors, and cylinders and addressed by logical block addressing (LBA).

The drive contains platters, a spindle, an actuator, and electronics. Magnetic encoding allows random access with latency tied to platter rotation.

Performance and storage density vary. Consumer drives commonly run at 5400 or 7200 rpm; enterprise models may run 10,000–15,000 rpm. Cache memory and interface influence speed. Technologies include PMR and SMR; helium-filled designs reduce windage and increase density.

Form factors include 3.5-inch desktop drives and 2.5-inch laptop drives; interfaces include SATA and SAS, with newer variants using PCIe in some architectures. Typical capacities range from hundreds of gigabytes to tens of terabytes.

Reliability: HDDs are mechanical and subject to wear, bearing or head failures, and contamination; S.M.A.R.T. monitoring tracks health. Lifespan varies with workload but often spans several years; backups and redundancy are recommended.

Use: HDDs remain cost-effective for bulk storage, backups, and archival data, and are common in desktops, laptops, NAS, and data centers. They are increasingly complemented by solid-state drives in many systems.