“Good backups are essential for every Mac user,” Joe Kissell writes for Macworld. “Tools such as Apple’s Time Machine, included as part of OS X, make it easy to store multiple versions of every file from your computer on an external drive or an AirPort Time Capsule. And if you want the security of off-site backups without having to physically move drives around, an online backup provider such as CrashPlan is a good option.”
“But while both these forms of backup serve important purposes, I also recommend maintaining a clone (also known as a bootable duplicate)—a complete, identical copy of your startup volume, stored on an external drive in such a way that you can boot your Mac from it if necessary,” Kissell writes. “What a clone offers that the likes of Time Machine and CrashPlan do not is immediate recovery: You can get back to work almost instantly after a drive crash or other severe problem with your startup volume. You simply attach your clone drive, restart while holding down the Option key, select the clone drive in OS X’s Startup Manager, and press Return. A few moments later, you’re back up and running—and you can then repair (or replace) your main startup drive more or less at your leisure.”
Kissell covers the pros and cons of the following apps:
• Carbon Copy Cloner
• ChronoSync
• SuperDuper
Much more in the full article – recommended – here.