Most people think that "failover is essentially automatic and magical." ☛ Michael Nygard's

 Depending on the detection and notification, there can be quite a delay before failover is initiated at all. (I once spoke with a retailer whose primary notification mechanism seemed to be the Marketing VP's wife.)
via  Wide Awake Developers Blog by Michael Nygard

I come from a systems management and operations background.  On a recent consulting engagement, I asked the tech leads what tools they used to monitor their production systems?  "None".  Well, I asked, how do you know when there is a production problem?  "The user calls us!"