Bin packing is the standard strategy that is used when merging
together data, it just writes the bytes of each flow file one after
another, inserting optional header, footer, and demarcators.
Defragment strategy is for when you have previously used one of the
"split" processors and want to undo the split back to a single flow
file. This mode requires that all of the incoming flow files have the
standard "fragment" attributes like fragment.identifier, fragment.index,
and fragment.count which are created by the split processors.