It was, with the exception of the Avaya, not actually expensive in hardware terms, a couple of thousand pounds to rectify, the major cost was downtime, a day until the building management got a generator in place and then two days to get their storage array up, running and restored.
It did have the nice side effect for us of selling them a full disaster recovery plan with additional testing days.
My point was that when you have a fault like this, it's probably best to find it before it becomes a real problem, could be as simple as a loose connection in a socket somewhere. .