Microsoft's most recent bulk file copy tool is RichCopy, in use inside Microsoft since early 2000'x, and released to the public in 2009 as an unsupported tool. It allows parallel file and directory copy operations, including normally not overwriting files if restarted unless file has been updated. (Can be changed using RichCopy options.)

Apparently RichCopy preallocates destination file space, which helps to cut down on file fragmentation. (If space was grabbed as needed, files would be intermixed)

As with most bulk copy tools, the tool floods disk access, making other disk operations rather slow.

for some other suggestions on tools, look at the wikipedia external links for richcopy.