Just curious, is there any way to use hard links and the like instead of raw copying to expedite the process? I noticed that the unsymlink-lib process chewed up a LOT of my I/O bandwidth doing copies and I was wondering if doing hard links on supporting filesystems would be easier on the disk. Or indeed anything else that would speed up the I/O.
Hard links have some breakage potential. The idea is that until --finish, the copy is pretty much disposable and the user can do anything about it, including modifying the files. The tool passes --reflink=auto to make use of reflinks if supported by the filesystem. This is the best optimization available, and it's safe as it doesn't force any data sharing between files.
