May I ask everyone what the meaning of redundancy is?

Three concepts should be distinguished: cold standby, hot standby, and redundancy. Cold standby means that the spare parts are purchased and stored in the warehouse; they are taken out when needed to replace damaged components, and the term “Backup” can be used to describe this concept in English ； Hot standby means that the spare parts are installed and powered on, but do not perform any tasks. It takes over automatically when the primary unit is damaged, just like in the case of two water pumps, one primary and one backup, as we usually refer to it. For example, the “redundancy” of I/O cards is usually hot standby, as only one card processes input/output signals at any given time. The “redundancy” of controllers in most DCS systems is also hot standby. This hot standby method requires a certain amount of time for automatic switching, that is, the time needed for the backup device to transition from standby mode to active mode; this time can range from a few microseconds to several minutes. True redundancy involves two or more identical components operating simultaneously; when one of them fails, the other components automatically take over the load that the failed component was handling, without any disruptions caused by a switching process. For example, in a DCS system, configuring two 24VDC switching power supplies is usually a redundant setup rather than a hot standby configuration. RAID5 in hard drive fault tolerance technology is also true redundancy. The triple controller used in Triconex’ ESD systems is also redundant, which is far more advanced than the hot standby controllers in ordinary DCS systems. However, please note that the \"redundant\" controller technology used in GE Fanuc’s ESD system involves two completely independent controllers handling tasks. Verification and coordination of the calculation results take place not at the controller level, but at the I/O level. This \"redundant\" approach presents a fatal flaw when it comes to exchanging information with external systems such as human-machine interfaces or DCS systems. This issue will not be discussed in detail here; it is mentioned merely to show that although they are both forms of redundancy, the specific ways in which they are implemented can lead to different performance outcomes. Redundancy is expressed in English as “Redundance”.