Apologies for delayed response, I'm guessing you won't see it, but...without Camus in place...did you do anything to ensure exactly-once semantics in moving the data to the Batch Layer?

For the real time layer I see it as not being mission critical for most data sets to be 100% correct, but for the ETL part of the process, the guarantees provided by Camus (ensured by the OutputCommitters part of MR I believe) are invaluable.