> Migrating old backups to Big Sur
I’ve previously used the tmutil command to migrate my backups, but that returned an error when I upgraded to Big Sur. How can I continue using my existing backups?
Big Sur offers two different forms of Time Machine backup: it can continue using the old format with backups stored in Mac Extended (HFS+) format, or you can start making a new backup set to a volume in APFS format. Whichever you choose, you’re better off archiving existing backups and starting a new set.
Apple recommends those running Big Sur should back up to APFS, which is free from many of the troubles which have afflicted Time Machine in the past. It’s also quicker and more efficient in its use of storage space. Unlike Time Machine backing up to HFS+ which can only copy whole files, when copying to APFS it only needs to copy those parts of large files which have changed since the last backup.
To still use old backups, set the Time Machine pane to make backups to that HFS+ volume. It should automatically detect it’s in old format and make old–style backups to it. You can’t convert those existing backups to the new APFS format; neither can older versions of Time Machine access its new backups to APFS.
WILL BIG SUR STILL SYNC WITH CATALINA OVER iCLOUD?
Yes. As far as we’re aware, macOS 11 hasn’t brought any changes in the features of, or support in, iCloud services or iCloud Drive. Some users have reported problems with Desktop and Documents in iCloud, but even those are rare.
WHAT IS AN .AAR FILE?
It’s a compressed archive format introduced with AppleArchive in Big Sur. Archive Utility can decompress them; Cormorant from bit.ly/ mac362aar both compresses and expands them for you.