You need a minimum of 5GB free space, and typically you need about 15% free space.
Your Mac needs adequate hard drive space to operate normally. A low amount of RAM requires more drive space for Virtual Memory’s swap files. Problems from insufficient RAM and free hard disk space are discussed in this link http://www.thexlab.com/faqs/lackofram.html
Look at these links.
Where did my disk space go?
Download & use *WhatSize* described in this link or Disk Inventory X @ http://www.derlien.com/
Freeing space on your Mac OS X startup disk
Amazing Disappearing Drive Space
Increase HD Free Space by using Monolingual @ http://monolingual.sourceforge.net/
How to free up my disk space
Where Did My Disk Space Go?
OS X 10.5.x can survive on small disks although efficiency may be reduced.
Several years ago I put a reduced OS X 10.4 on a 2 GB memory stick for emergencies.
I still have full Leopard versions on 4 GB and 8 GB partitions.
I have always found it difficult to justify the need for a percentage of free space. As an Engineer I would like to see a calculation which justifies it.
To facilitate testing of various OSs my 120 GB main disk is split into 2, 4, 8 and 5 off 20 GB partitions. My working OS 10.5.8 with all files and 15 years POP email occupies 12 GB on one of the 20 GB partitions. Everything is regularly backed up to several 750 GB disks. Approximate sizes of folders on this working OS are:
- 2 GB - Applications
- 1 GB - Developer
- 1 GB - Library
- 3 GB - System
- 3 GB - Users
- 2 GB - Other