Disk Full!

I usually use Linux boxes for my work and hobby(?). One machine got
troubled today. Debian is installed in it, and recently it was
updated to a new version "sarga". I didn't know it and upgraded by a
command through Internet. The machine has only a small HD, so disk
full caused error during the update... Now the machine is almost
recovered. But is it better to use more large HD? Ummm...