Hard Drive

A hard disk drive is a magnetic storage medium used for the permanent storage of data. Data is written to rotating magnetic platters that are accessed by moving read and write heads. Common form factors are 3.5 inch for servers and desktop systems and 2.5 inch for laptops and compact storage bays. Hard disks are connected via SATA, SAS or legacy interfaces such as SCSI. Key characteristics include capacity, rotational speed, cache size and suitability for continuous operation, as found in enterprise and NAS models. Compared with SSDs, hard disks offer lower cost per terabyte at slower access speeds. They are therefore mainly used for archiving, backup and large data volumes. In servers and storage systems, RAID configurations provide resilience and higher throughput.