Daring Fireball: An Ode to DiskWarrior, SuperDuper, and Dropbox
I have learned this the hard way (via 43 folders).
"However, I find terrific value in SuperDuper’s model. SuperDuper creates a bootable clone of your startup drive. With Time Machine, if your startup drive goes kaput, you’ve got to go through a lengthy restore process (and, in the case of hardware failure on the kaput drive, you need an extra bootable volume to restore to). With SuperDuper, you just plug in the clone, reboot, and you’re back up."
Outstanding comprehensive how-to from John Gruber.
Hard drives are fragile. Read as much as you can bear to about how they work, how incredibly precisely they must operate in order to cram so many bits onto such small disks. It’s a miracle to me that they work at all. Every hard drive in the world will eventually fail.