On April 21, 2011, Amazon's Elastic Compute Cloud went down when a planned upgrade was "executed incorrectly":
The goal "was to upgrade the capacity of the primary network," Amazon says. "During the change one of the standard steps is to shift traffic off of one of the redundant routers in the primary EBS [Elastic Block Store] network to allow the upgrade to happen. The traffic shift was executed incorrectly and rather than routing the traffic to the other router on the primary network, the traffic was routed onto the lower capacity redundant EBS network."Read the full article at Network World.
Ultimately, this meant a portion of the storage cluster "did not have a functioning primary or secondary network because traffic was purposely shifted away from the primary network and the secondary network couldn't handle the traffic level it was receiving."