Learn in the textbookReliability Design
DefinitionHot standby (ホットスタンバイ) keeps the standby system already running so that it can take over the moment the primary system fails.
ExplanationThe standby system is powered on, with the programs it needs already up and running. Switching over therefore takes little effort, and users see only a very brief interruption. The trade-off is the cost of keeping the equipment running even while it waits.
AnalogyLike a taxi idling at the stand with its engine on, it can pull away the instant someone hails it.
Memory hookHot means already warmed up, so the machine can go right away.