RSync Large Folder on Windows

[Matt McCutchen]

Brad, I would recommend itemize and double-verbose (rsync -ivv) to get
more information about why rsync is transferring and/or skipping
files.  You also might try --modify-window=1 or maybe 2.  If none of
that works, you can always try upgrading rsync.

Regarding -u: Under the default quick-check rule, rsync always skips
transferring a source file if the destination already has a file with
the same size and last-modified time.  -u is used only to stop older
files from overwriting strictly newer files, perhaps because the newer
files are about to be sent back the other way.

Matt