John Gruber has exactly the right prescription:
- Do a complete backup clone to an external FireWire drive.
- Test that the backup is indeed bootable and up to date.
- Unplug the backup drive.
- Boot from the installer DVD and perform a default upgrade.
This is how I’ve done the last few upgrades, but when my copy of Leopard arrives next week I think I may do a clean install. I haven’t done one for many years, and there’s probably lots of accumulated sediment… I could do with a spring clean.
I’m only really doing this because I’d like to stop running my machine with its disk 98% full! I regularly use OmniDiskSweeper to find and remove major space-hogs – video podcasts that I watched long ago and forgot to delete, for example. And I long ago moved most of my photos and videos to external drives. But now I suspect it’s the thousands of smaller files – logs from utilities I tried under 10.3 and such – that make a significant contribution… We’ll see… 100GB ain’t what it used to be…