In a perfect world we would never have to worry about burglary, fire or, Heaven forfend, asteroid strike. Our concerns would be making sure that our project was going well, that the latest upgrade hadn’t messed up our libraries and that we had correctly formatted that email to MacTalk.

Unfortunately, “Murphy is driving the bus” and anything that can go wrong will go wrong if we wait long enough. A backup is there to get your device back to the state it was in before the drive failure or asteroid strike. (A hard drive failure is inevitable, the asteroid strike is a lot less likely, so keep calm and carry on). To this end you need to have a bootable copy of your system; some record that will allow you to plug it into a computer, press a few buttons and be back with all your programs running and settings enabled and to do all of this without losing the last article you typed or that latest batch of selfies.

At least, you should use Time Machine to keep up to date with changes to your data but be aware that Time Machine does not produce a bootable copy, you’ll need a computer with an operating system already installed.

Having mentioned that backups are needed, what exactly are we talking about?
I should mention Time Machine will be of no use if you carry it out on your current hard drive and that is the drive that fails. The backup needs to be on a different drive.

For full recovery, you also need a bootable backup, or clone, which will get you onto a blank machine and there are a number of applications that will do this. This, too, should be on a separate drive and should, ideally, be stored away from your main computer – the asteroid strike is unlikely but not impossible.
iCloud is a useful way to have your backups stored off-site, you don’t get much more off-site than a nebulous, nobody-knows-quite-where storage facility.
Ideally you should have all three backups running on a routine that you stick to.

How often to backup depends on how important your data is. If, like me, you just store family photos, music and a few unimportant pieces of text, then a full backup every time you make a significant addition to your photo library or import a CD will suffice.
Someone running a hobby Web site or carrying out lots of research for fun may do weekly, or monthly backups.
Businesses should definitely run their backups every day.
Only you can decide how precious your data is, how many hours you are willing to expend on recovery and what the cost (in time as well as money) will be.

And always remember that just because you have run the backup doesn’t mean it will work – test every backup as part of the routine. A backup to a broken drive is an expensive paperweight.

Fred Dowson