You can replace a power supply unit (PSU) as a hot-swappable server component. The server can operate on a single PSU if necessary, making it possible to replace a failed PSU without shutting down the server. If a PSU fails, it must be replaced as quickly as possible because operating on a single PSU means that there is no redundancy in that area, increasing the risk of an interruption in service to clients.
LED indicators on each PSU indicate the PSU status.