Add an option -count to distcp for displaying metadata about src files like number of files to be copied and total size of src files to be copied.
WIth -count, distcp doesn't do any copy. Just displays info and exits.
This is useful specifically when used with -update.
distcp -update -count <src>* <dst>
would display the number of files to be updated and the total size of copy needs to be done(by comparing the file sizes and checksums at src and dst). Based on this info, users could allocate the number of nodes needed for the actual update job.