Hot Swapping,What is SWAP

Hot Swap

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 and hot plugging are terms used to separately describe the functions of replacing system components without shutting down the system. Hot swapping describes changing components without significant interruption to the system, while hot plugging describes changing or adding components which interact with the operating system.^[1] Both terms describe the ability to remove and replace components of a machine, usually a computer, while it is operating. For hot swapping once the appropriate software is installed on the computer, a user can plug and unplug the component without rebooting. A well-known example of this functionality is the Universal Serial Bus (USB) that allows users to add or remove peripheral components such as a mouse, keyboard, or printer.

Reasons for hot-swapping

Hot swapping is used whenever it is desirable to change the configuration or repair a working system without interrupting its operation. It may simply be for convenience, to avoid the delay and nuisance of shutting down and then restarting complex equipment, or because it is essential that the equipment be permanently available.

Hot swapping may be used to add or remove peripherals or components, to allow a device to synchronize data with a computer, and to replace faulty modules without interrupting equipment operation.

Equipment may be designed with redundancy so that in the event of the failure of a component, other parts of the system carry out its functions while the faulty component is removed and a replacement connected. For example, computer RAID disk arrays allow a faulty disk to be hot-swapped for a new one; the new one is configured to become part of the array automatically or by user command. A machine may have dual power supplies, each adequate to power the machine; a faulty one may be hot-swapped.

Hot Swap: A true hot swap is defined as one where the drive can be replaced while the rest of the system remains completely uninterrupted. This means the system carries on functioning, the bus keeps transferring data, and the hardware change is completely transparent.

Warn Swap: In a so-called "warm swap", the power remains on to the hardware and the operating system continues to function, but all activity must be stopped on the bus to which the device is connected. This is worse than a hot swap, obviously, but clearly better than a cold one.

Cold Swap: The system must be powered off before making the swap.