There are a number of different ways of making a backup of your Mac. You could manually copy just your documents to a CD-R, and if you had a hard disk die you would then have to install Mac OS X on a replacement drive, install all your applications, update everything, copy your documents back from the CD-R and go through setting all of your preferences again. If your time is worth nothing to you then that could be a perfectly viable backup option. However for virtually all of us our time does have an opportunity cost, instead of doing all of the above you could be creating work that you are charging a client for, playing with the kids or walking the dog. Just because you aren't charging out your time it doesn’t mean that it is worth nothing.

Traditional backup programs such as Retrospect take the approach of backup up the items that you specify, which could be your entire computer, to some medium and then backing up any changes to that medium on a scheduled basis. In order to work out what changes have been made Retrospect needs to compare what it has backed up with what is currently on the disk, and this can take a while. Also if you had a disaster and needed to replace your Mac's drive you would then need to restore everything from Retrospect's backup. Depending on what medium you backed up to and how long it is since you last did a full back up this can take a lot of time.

Time Machine is integrated into the Mac OS and uses a technology called FSevents to check when a directory on your Mac has changed. If that is a folder that Time Machine will be backing up it can quickly check to see what files have been changed rather than having to scan the whole drive for changes. Time Machine is quick to find the files that need to be backed up and restoring a single file can also be relatively quick. To restore a full system from a Time Machine backup you can boot from your install DVD and then from the Utilities menu choose "Restore System from Backup".

The downside of both Retrospect and Time Machine is how long it takes to get up and running again if you have a hard drive that dies on you. With both programs you have to restore your data before you can get back to work. An alternative is to create a copy of your drive, with all your data, the OS and programs on, which you can start your Mac up from. Using either Carbon Copy Cloner or SuperDuper you can create a clone of your Mac to another drive and if your hard drive fails all you need to do is to boot your Mac whilst holding down the Alt key and then select the backup as your start-up disk and be instantly working again. Something to bear in mind is that you are now working from your backup and so essentially you have no backup at all at this point but it will get you out of a real hole if you have a hard disk failure at a critical time.