Back up your Mac
Backups are vital in case you lose files or need to migrate
Like insurance, backing up before upgrading is essential to ensure you don’t need those backups: when an upgrade goes well, they should seem a waste of time and effort. But try skipping them, or relying on old or incomplete backups, and when something does go wrong you’re likely to lose hours or days as well as some of your most important files.
Backups made before upgrading to Monterey cover three potentially sticky situations. While the installer will always try to join up the new System with your existing Data volume, that may not work out, in which case you’ll need to migrate your documents, apps and other files from your copy or backup.
Updates also bring a lot of reorganisation, in the process sometimes dumping files into folders of relocated or rescued items. Your backup enables you to restore anything that goes missing during or after the upgrade, and to discover where any relocated items came from.
And in the unlikely event of total disaster, if you do need to abandon your attempt to upgrade and retreat to your previous version of macOS, that will only be possible using your backup.
Existing backups
If you’re already backing up with Time Machine to Apple’s new file system APFS in Big Sur, then Monterey should try to continue making those backups in continuity, as they’re fundamentally compatible. However, if you’re currently backing up to storage using the Mac Extended file system HFS+, using any version of macOS, you should archive those backups, ideally by replacing your backup storage for fresh, and prepare to start a new series of backups using Monterey.
If you’re backing up using a thirdparty utility, such as Carbon Copy Cloner, SuperDuper! or ChronoSync, ensure you’re using the current version before you upgrade, and check its support site for information about compatibility with macOS 12 before even starting to move. Backing up to network storage also requires careful consideration,
although if you’ve already been doing that from Big Sur, Monterey shouldn’t bring any surprises.
The question of whether you should make backup copies of the System is more complex, and depends on your Mac model. For Intel Macs without a T2 chip, apps like Carbon Copy Cloner and SuperDuper! can make potentially useful copies of the System in Big Sur and earlier. With a T2 chip, those are only usable if you change startup security options to allow booting from the external drive containing the older version of macOS.
M1 Macs are different again. Although you can clone the System to an external drive and use that to boot from, an M1 always begins to start up from its internal
SSD, and it’s not a wise choice to try booting from an external drive and cloning that back to internal storage. The most reliable plan with an M1 is always to use one of Apple’s installers to install the System on a drive, and not rely on the process of cloning, even though that might still work.
If you’ve got storage available, when you’ve completed your backups you should have one normal backup, perhaps made by Time Machine, and a separate copy of the data on the drive you’re going to upgrade, made using a different method. Those are your insurance policy: whatever you do, keep them safe until you’re completely confident that the upgrade hasn’t quietly done away with anything significant.