Just reading about major performance impacting storage load issues on the Rackspace cloud in their DFW data center that have been dragging on (what is it with DFW anyways?).
This isn’t rocket science guys, find the host with the most traffic to the SAN, find the virtual on that host with the most traffic to the SAN, and throttle it or kill it. Repeat as required. This is a great example of what happens when you don’t build traffic monitoring into your cloud.