<reliability> Automatically switching to a redundant or standby server,
system, or network upon the failure or abnormal termination of the
currently-active server, system, or network (a "hot standby" or "warm standby").
Failover happens without human intervention. This feature is usually built-in to
expensive systems which must be available continuously.
factor « factorial « FAD « failover » failure
» failure-directed testing » FAIR