Regardless of how much data you think you have, things will change over time. New projects will pop up and data creation rates for your existing projects will change (up or down). Data volume will usually ebb and flow with the traffic of the day. Finally, the number of servers feeding your Hadoop cluster will change over time.
There are many schools of thought on how much extra storage capacity you should keep in your Hadoop cluster (we use the totally unscientific value of 20 percent, which means that we usually plan for 80 percent full when ordering additional hardware but don't start to panic until we hit the 85-90 percent utilization number). Generally, you want to keep enough extra space so that the failure and/or maintenance of a server or two won't cause the HDFS block replication to consume all the remaining space.
You may also need to set up multiple flows inside a single agent. The source and sink processors are currently single-threaded, so there is some limit...
