A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnetic material. The platters are paired with magnetic heads, usually arranged on a moving. The first production IBM hard disk drive, the, shipped in 1957 as a component of the IBM 305 RAMAC system. It was approximately the size of two large refrigerators and. The highest-capacity HDDs shipping commercially as of 2025 are 32 TB. The capacity of a hard disk drive, as reported by an operating system to the end user, is smaller than the amount stated by the manufacturer for several reasons, e.g. the operating system using. IBM's first hard disk drive, the, used a stack of fifty 24-inch platters, stored 3.75 MB of data (approximately the size of one modern digital. The factors that limit the on an HDD are mostly related to the mechanical nature of the rotating disks and moving heads, including: Due to the extremely close spacing between the heads and the disk surface, HDDs are vulnerable to being damaged by a Magnetic recordingA modern HDD records data by magnetizing a thin film of on both sides of a disk. Sequential changes in the. Current hard drives connect to a computer over one of several types, including parallel,,, (SAS),.
