Just to be clear the Airport Extreme (AE) has no hard disk.. the Time Capsule (TC) is the same case now with the same basic board, but does have a hard disk inside..
They are different and it makes it easier to be clear they are different. No mixing up the names..
TM is designed to store files as they change.. and keep storing them until the disk is full. Even if your hard disk in the Mac is 500GB.. you cannot only use 500GB for the backup.. you need at least 3 times the space actually used.. and more if possible.
You also cannot partition the TC.. it is not designed to work as a NAS.
If you press it into this function.. please be aware of the following..
1. Any files stored only on the TC are at risk .. you must back up the TC.
2. The TC has no built in backup.. it is a backup target for Time Machine .. but Time Machine cannot backup network drives.
3. It is not good to mix TM backups with files.. it is possible to keep them separate.. even though you cannot partition by using a dmg file.. see
Q3 here. http://pondini.org/TM/Time_Capsule.html
4. Do not use applications on the computer with live files on the TC.. it is fine to backup your files.. but running live (currently edited files over network to a TC is a good way to lose them).
5. If you still us iphoto Apple has specific instructions not to keep the library on network drives.. new photo app is still a bit more of a mystery.
Good luck.
