How are you dealing with bit rot? Are you periodically scrubbing the data to give the controller a chance to repair or are you waiting to get a URE during an array rebuild? Are you running end to end checksums against all your data to protect against bad firmware, bad ram, etc. What is your mean time to repair in case you lose a drive?

One more question: you saturated the network link with a sequential read/write, but is that how you actually store the data? If not, how long would it take you to be up and running on another CDN in case Akamai goes down in flames?