So the sewer tank/pump situation is like this:
-- we had two 1/4 hp pumps in there
-- both still work
-- either alone can't pump all the way up to the street. they try really hard but only make it up to the garage.
-- no clogs anywhere
-- pumping together, they can make it
-- we lost half the power outlets down there (GFI tripped and now broken, won't reset), hence the failure: one pump stopped pumping, and other couldn't handle it alone
So much for redundancy! So we always needed both. There was never a "backup" pump.
Replacing them, at a lovely cost, with 1/2 hp pumps.
This, folks, is why active-active database configurations are a bad thing... because people are too lazy to verify that they're only using 50% or less of capacity on either side. Then all the sudden you need 70% of each side, and you're surprised when one fails and the other can't handle 140%.
But this sewer situation is even more depressing than databases because the load (heh) doesn't increase over time... it's pumping 20-30 feet of head always, or it's not pumping at all.