A hot swap is the replacement of a hard drive, CD-ROM drive, power supply, or other device with a similar device while the computer system using it remains in operation. The replacement can be because of a device failure or, for storage devices, to substitute other data.
Hot swapping works by providing a rack or enclosure for the device that provides an appearance to the computer's bus or I/O controller that the device is still there while it's being removed and replaced with another device. A hot swap arrangement is sometimes provided where multiple devices are shared on a local area network. Hot swap arrangements are sold for both SCSI and IDE hard drives. Hot swap versions of a redundant array of independent devices ( RAID ) are also available.