Back Up Your Mac with External Hard Drives
To prevent the loss of all your data if your Mac’s hard drive should suddenly bite the dust, you can connect an external hard drive to your Mac’s USB or Thunderbolt port with a cable that’s typically included with the hard drive.
USB and Thunderbolt ports connect peripherals to a computer. USB ports commonly connect a mouse, printer, or digital camera. Thunderbolt connects a display or storage device. The main advantage of using external hard drives is that copying large files is much faster and more convenient than copying the same files to CDs or DVDs.
Additionally, external hard drives are easy to unplug from one Mac and plug into another Mac; plus, only one of the newest Mac models even has an optical disc drive.
You can also put an external hard drive on your network. For example, Apple’s Time Capsule provides external storage and functions as a Wi-Fi hub so multiple computers can back up to the Time Capsule. (There are 2TB and 3TB (terabyte) versions, so you probably won’t have to worry about storage space.) Any networked drive must use Apple File Protocol (AFP) file sharing.
Perhaps the biggest drawback of using external hard drives is that they can’t protect against a catastrophe near your computer, such as a fire burning down your house or a flood soaking your computer desk and office. If a disaster wipes out the entire area around your computer, your external hard drive may be wiped out in the catastrophe as well.
You can treat an external hard drive as just another place to copy your files, but for greater convenience, you should use a special backup application, such as Time Machine. Backup applications can be set to run according to a schedule (for example, to back up your files every night at 6 p.m.)
If the files haven’t changed since the last time you backed them up, the backup application saves time by skipping over those files rather than copying the same files to the external hard drive again.
To retrieve files, you could just copy the files from your external hard drive back to your original hard drive — but be careful! If you changed a file on your original hard drive, copying the backup copy can wipe out the most recent changes and restore an old file to your hard drive, which probably isn’t what you want.
To keep you from accidentally wiping out new files with older versions of that same file, backup applications always compare the time and date a file was last modified to make sure that you always have copies of the latest file.