If I had “terabyte sized” files to deal with, then I would try mightily to avoid copying them at all.   It is well worth whatever effort it might take, IMHO, to build a list of filenames, and to arrange for whaever program it may be to switch from one file to the next.   I say this, not merely because of the time required to copy the data, but also the unwieldy unmanageability of such a large contiguous single file.