Earlier, we said our Mac folks should upgrade to Leopard “if and only if [they] have good backup.”

We do not mean by this that you can expect to NEED said backup if you try to update. Our upgrade went swimmingly well. We just mean you should NEVER EVER EVER do something like that to your computer (and kind, be it Mac or PC or Linux or VMS or whatever else you freaks are running) without having a complete, solid, and up-to-date backup on hand.

Go buy an outboard drive as big as your computer’s internal drive. Actually, get two. They’re cheap. Shut up. As JWZ said a while back, listen to me. I know things.

Then go get some kind of smart hard drive cloning tool. On the Mac, I like SuperDuper (which is presently broken under Leopard, but works fine for 10.4 and below; also, its “brokenness” doesn’t keep you from reading your backup, just updating it). CarbonCopyCloner is also a fine choice. On the PC, I’ve no personal knowledge, but LifeHacker liked DriveImage XML despite its cheesy name.

These tools will create, on your backup drives, a complete (and potentially bootable) copy of your machine’s hard drive. Typically, your first backup will take many hours, but subsequent ones will copy only the new or changed material; expect those to run for maybe an hour. Why two drives? Because that way you can alternate. Do a complete system backup like this every week, and swap the drives every month. Put the drive you’re not backing up to someplace else. Your spouse’s office is a good choice, or a friend’s house.

Sound like overkill? It’s not. Imagine the tax records, the digital pictures, the emails, the documents and God knows what else that were lost in New Orleans or the Mississippi coast. Imagine how smart you’ll feel if, God forbid, something like that happens where you live, but you’ve got a month-old backup at your mother-in-law’s place, safe and sound. Imagine how little effort this takes.

Of course, this is just system backup. Your critical files should ideally be backed up every day using another mechanism, like one of myriad online backup tools now available. People seem to like Mozy, for example. No reason not to join them. It’s cheap, and it works. What more do you want?

Now, go forth. Backup. Always.

(“Hey Chet, what about Leopard’s Time Machine?” Glad you asked. It’s a great idea. Buy a third drive to use for TM. It doesn’t replace the need, in my opinion, for full-disk bootable backups, or for frequent offsite saves of critical stuff (i.e., your Documents folder).)