I don’t know if you’ve looked at Apple’s current guidance for macOS Mojave on backing up your Mac, and I’m grateful to Al Stonebridge, my former editor-in-chief at MacFormat, for drawing attention to its howlers. Included in its list of “alternatives for backing up your Mac” are iCloud Drive, CDs and DVDs, and backing up from one partition to another on a single hard disk. I’m shocked that Apple should be giving such advice, and lending its endorsement to such dangerous practices.

Backing up is about preserving your files and data in the event of losing access to your working copies. It’s a matter of compromise between risk, reliability, convenience and cost.

We’re notoriously unreliable at assessing risk, but you have to plan backups around it, and cater best for the most common events like inadvertently trashing files, while also preparing for the more unlikely disasters like your office/studio/house being totally destroyed. Backups are most convenient when they’re immediately to hand, on a storage system connected directly to your Mac. When a crucial document goes missing, it’s quick and simple to find a backup of it, and a minute or two later you’re carrying on with your work.

macOS has an even more convenient system for storing recent versions of many documents (for apps which support it) in its version manager. That has saved me so much work on so many occasions, but it isn’t a backup as such, and is no substitute for maintaining proper backups. It can also prove disappointing at times: as with everything else, when you most need an old version, it is often nowhere to be found.

I also make working copies of documents I am developing to my iCloud Drive, for example when I’m writing an article for a magazine. This is to give me a means of rapid recovery in the event that the Mac I’m working on becomes temporarily unavailable, perhaps as a result of hardware failure. Whether these should be considered to be true backups is a matter of semantics. They’re only a small part of my backup strategy, as they rely on storage over which I have no control.

Backing up to iCloud seems very attractive because it’s off site. If my Time Machine backups were to be destroyed, the documents stored on my iCloud Drive would be invaluable, as all I’d need is to connect to my iCloud account and I could access everything stored there. Except that I need to be able to connect to a service which I don’t control. Some Catalina beta-testers have discovered that the latest beta release (including the public version) has wreaked havoc with their iCloud Drive, and that they have lost data from it. Other (non-beta) users have gone to where they assumed iCloud backups to be, only to discover that there was nothing there at all.

There are dedicated cloud backup services which have become popular solutions for many businesses. They’re quite different from iCloud, being dedicated to and operated for offsite backup. iCloud is a consumer service which supports a wide range of different uses, and comes with no guarantees over the integrity or accessibility of data stored there.

Apple’s terms and conditions of service state, with the original capitalisation:
“Apple shall use reasonable skill and due care in providing the Service, but, TO THE GREATEST EXTENT PERMISSIBLE BY APPLICABLE LAW, APPLE DOES NOT GUARANTEE OR WARRANT THAT ANY CONTENT YOU MAY STORE OR ACCESS THROUGH THE SERVICE WILL NOT BE SUBJECT TO INADVERTENT DAMAGE, CORRUPTION, LOSS, OR REMOVAL IN ACCORDANCE WITH THE TERMS OF THIS AGREEMENT, AND APPLE SHALL NOT BE RESPONSIBLE SHOULD SUCH DAMAGE, CORRUPTION, LOSS, OR REMOVAL OCCUR. It is your responsibility to maintain appropriate alternate backup of your information and data.”

This applies particularly to storing your Desktop and Documents folders in iCloud, a practice which I have consistently condemned since it was first introduced. I have this enabled on the MacBook Pro on which I am currently running Catalina; it wasn’t particularly reliable before, and now is just an unholy mess.

Copying files from one partition/volume on storage to another partition/volume on the same storage system isn’t backup at all, nor should users ever consider it to be part of a backup system, particularly on a hard drive. Going back to the issue of risk, one of the commonest reasons for wanting to restore from a backup is when your Mac’s primary storage has failed, or has had to be replaced as part of repair – something which is increasingly common as Apple solders more SSDs in. If your backup is on the same physical device as the files which it purports to copy, then both copies of those files are equally exposed.

There are those who claim that some degree of protection is better than none. Unfortunately, that’s not the way that most humans work. Once you’ve started backing up to the same drive, you’re likely to rely on that false protection, until loss of the drive finally demonstrates what was obvious all along: copying files to the same storage isn’t a backup. Not at all.

When you’re designing your backup systems, you need to think in depth. Cater for the immediate, to ensure that you can restore the whole of your Mac as quickly as possible, and that everything of any importance also has copies stored off site. Think through how your system can cope with different scenarios, from trashing your tax return a few hours before you’re due to file it, to rebuilding your life after all your computer gear has been destroyed. One size won’t fit all, but a layered solution usually does very well.

You may also have noticed that I haven’t yet mentioned another of Apple’s recommendations: CD/DVD disks. That’s because it must be over five years since Apple last shipped a Mac with a built-in optical drive*, and trying to back up 100 GB and (much) more to DVDs is worse than tedious and thoroughly unreliable.

* Thanks to Andy Norman for pointing out that one model, the last non-Retina MacBook Pro, did continue to ship until October 2016. However, that was an odd exception to Apple’s policy of dropping optical drives. And I’d love to see anyone successfully back up 1.2 TB to DVDs!