There’s nothing like discovering that your MacBook Pro wants to die after upgrading to Yosemite, and that it’s failed to alert you to the fact that Time Machine hasn’t backed it up successfully in over 20 days. It’s been getting progressively worse over the past few weeks. It started as slow app launch times, and moved onto painfully slow OS launches, unresponsive Finder and Spotlight on boot, and more.
If you rely on Time Machine backups, make sure you’re routinely verifying that a backup has, in fact, taken place. I had assumed my backups were current. I was wrong. System Preferences > Time Machine will report the date and time of your last successful backup. You can also browse backups by entering Applications > Time Machine, or browsing your backup diskand going to Backups.backupdb > Computer Name > and look for a series of dated folders. It’ll match this format: YEAR-MO-DAY-TIME.)
If your Mac fails to backup at any time, you can always try deleting any .inProgress files that happen to be located in the same folder as the dated ones and try initiating a backup again. (Under Yosemite, you have the option of assigning multiple hard drives as Backups and Time Machine will alternate between them.)
Don’t rely on Time Machine to be your only backup solution. SuperDuper! for Mac (Free/$27.95) can easily make fully bootable backups. (The paid version will even allow you to schedule full backups.) Carbon Copy Cloner 4 ($39.99) is another viable option, though I haven’t used it personally.
You can get a 1TB drive for less than $60 on Amazon (affiliate link).
I’m lucky I have semi-recent backups. But it could have been much worse. There’s no reason you shouldn’t be backing your system up regularly. Be prepared for the worst case scenario.