If you have a Mac and you've suffered a hard drive failure, your search for the term "data loss" or the like has brought you to this article for a reason, so please read on. I promise I'll get to the point.
How do you classify different computer users? How many kinds are there in the world?
Would you go by skill or experience, like Beginner, Intermediate, Advanced? Would you classify them by the type of computer they use? Windows/Mac/UNIX, etc? Nope. The answer, my friends, is two. There are ONLY TWO groups of computer users in this world, and you must always remember who they are:
Group #1 are those users who back up their data.
Group #2 are those users who wish they had.
That's it. Simple, right? I impress this on all my students. Unfortunately, we've all be in that second group at some point, especially those of us who've been using computers a long time. Losing one's data is never exactly pleasant, and it can range from the annoying to the catastrophic.
Regular data backups should be a habit. Since the release of Apple's OSX 10.5 (Leopard) they have included a built-in tool for performing regular and automatic backups called Time Machine. All it takes is an additional external drive (which I suggest is at least twice the capacity of the sum of every drive you want to back up).
Time Machine makes it very easy to retrieve trashed or previous versions of files, or even restore the entire system if your internal drive fails. With the price of large-capacity hard drives nowadays, there's really no excuse for not backing up your data regularly.
Now with all this said, remember this is an emergency plan that will keep you safe if the drive that runs your Mac fails. You simply install a new drive and restore the entire system from your Time Machine drive. But if there is a physical catastrophe like theft or damage to the Mac and the backup drive, you may be in for a rough time. So for complete peace of mind, an online cloud backup service might be desirable, at least for your most important data. The two cloud storage services I can recommend without reservation are Backblaze and Dropbox.
Also remember Apple can store your passwords, contacts and calendars, up to so many pictures, etc. online in iCloud, but this is limited to *only certain data*. I can't stress this enough - iCloud is made for syncing between your devices or sharing photos with others. It is not a comprehensive data backup service. To upload all the data of your choice, you'll need a cloud storage service as mentioned above.
Be safe, back up and happy Mac'ing!
The Mac Doc