Before mirroring a complete Ubuntu / Debian repository on your hard drive, you want for sure have an estimation of the "weight" of all packages.
This script computes the total size of various Debian-based repositories by means of downloading the Packages.gz and making a sum of the size of every package. Of course, there are many shared packages between different versions of the same Linux distro. So this script will compute the max possible size.
I got the following results:..
Summary [Feb 9, 2012]
UBUNTU TOTAL SIZE = 466993 MB [456 GB] *
DEBIAN TOTAL SIZE = 184712 MB [180 GB] **
DEBIAN-SECURITY TOTAL SIZE = 22148 MB [21 GB] **
DEBIAN-VOLATILE TOTAL SIZE = 489 MB [0 GB] **
TOTAL SIZE: ~658 GB
* Considering lucid, maverick, natty, oneiric and precise, with i386 and amd64 architectures, and the components main, multiverse, restricted and universe
** Considering lenny and squeeze with i386, amd64, armel and arm architectures, and the components main, contrib and non-free