hard disk

A recording medium that uses one or more disks with magnetic surfaces stacked on top of each other, and reads and writes data using a magnetic head while rotating the disks at high speed.

It is very convenient as a large-capacity storage medium, and therefore is used in most computers.

The distance between the disk and head is very narrow, and therefore it is vulnerable to shocks and has a high possibility of failure.
In servers etc., RAID (Redundant Arrays of Inexpensive Disks) systems are used to ensure more reliable and robust operation for use as a storage medium for important data.

→ See RAID