The problem is that RPM is a compressed format. Change one byte in
it and
there are chances ALL the remainder of the file is different. One thing
gzip can be patched to avoid this. Debian have done so for apt/dpkg (Rusty
did a talk on this). It was tried ages ago but caused a problem that should
now be fixed.
Another big problem for the ftp sites is that rsync is relatively cpu/mem
intensive so 3000 parallel rsyncs isnt too cool