A Few Thoughts On The Dangers Of Time Machine

I haven’t lost a document or file on my Mac in many years because I have a good, dependable, multi-hard disk backup plan.

Plus, I sync valuable files between Macs and copying some files off premise, away from home and office. Like many Mac users, I welcomed Time Machine as a handy complement to my backup strategy.

There’s just one problem with Time Machine. Yes, once you set up Time Machine on an appropriately sized hard disk, it just works. Time Machine backs up all your files, then backs up files that have changed.

Time Machine is truly a set it and forget utility. It works. Yes, right after Leopard’s launch, some of us had problems with hard disk size, and some disks that didn’t play nice nice with Time Machine.

But once I got it set up on a couple of Macs, it just worked. After a week or so I checked back in time to see files I had deleted were still stored in Time Machine. Great. What me worry?

I backup Documents, Music, Photos, and other files regularly using ChronoSync, and regularly clone my Mac’s hard disks using SuperDuper! (still not ready for Leopard), so Time Machine was a no cost extra way to track and find files.

Did I mention that it just works. Your mileage may vary, of course, but Time Machine as been as Apple said. “Set it, then forget it.” Therein lies the rub. I forgot about it.

Time Machine continually monitors your Mac’s files. Every hour, every day, incremental backups are made. Hourly backups to days. Daily backups for the past month. Weekly backups for anything older than a month. If you create and then delete a file before the next hourly backup, that file won’t get backed up.

Time Machine has a few options. You can select a specific hard disk to use for Time Machine’s backups. You can also exclude certain files or folders you want to skip in the backup process, so there’s some level of control. If you go to the trouble.

My guess is that most Mac users, me included, simply got Time Machine running, checked it out, found that it worked OK, then forgot about it.

The other day I was checking my Mail inbox, deleting some messages, moving others. On a whim, I clicked on Time Machine to see what it would show me. There it was in the Time Machine window—nearly a month of Mail inboxes streaking back in time on my Mac.

So I checked the inbox from two weeks earlier. Guess what? All those email message I thought I had deleted were still there, biding their time in Time Machine.

Uh oh, I thought. What else is Time Machine keeping that I really don’t want to keep? Not only does Time Machine keep every Mail message it can find, even those you thought you deleted, it also remembers Safari bookmarks.

Yep, the Safari Bookmark plist file from weeks ago remained intact, dutifully saved each day by Time Machine. How about Safari’s History plist? Time Machine saved that, too.

You may have thought you cleared Safari’s History or cleared out some bookmarks, but they’re still in your Mac, protected by Time Machine for posterity.

Therein lies a basic danger in Time Machine. Set it and forget it. Except that Time Machine doesn’t forget it, leaving on your Mac some information which could be sensitive, embarrassing, even dangerous. Information you thought had been deleted, but wasn’t. That Guest account in Leopard is looking awfully good, huh?

Time Machine requires a big hard disk, and a big disk means a huge number of files can be stored. Whether those files are valuable, useless, or dangerous, Time Machine doesn’t care. With the good comes a little bad.

Is it time for Mac software developers to find a way to prune some of Time Machine’s hourly and daily collections with an handy utility? Yes. I’m up for that. How many Mac users know where their Safari bookmarks and history files are kept? How many would know how to set up Time Machine so that it does not backup deleted Mail files?

I love Time Machine, but I’m beginning to see a need to exercise some caution when Apple provides Mac users with a “set it, then forget it” feature.