I have hard linked Fedora 21,22,23,24 over to /pub/archives/fedora and /pub/archives/fedora-secondary. Next week I will work with Adrian to have mirrormanager to point to the archived version and then I will remove them from /pub/fedora and /pub/fedora-secondary. This should cut down the mirror size quite a bit.
I will also work with releng to have any old development 26 directories cleaned up also.