Each container has one or more volumes, and each volume (starting in High Sierra) has a “role,” which defines the kind of volume it is. APFS divides a disk into one or more containers (similar to partitions). Not only must you use Big Sur to back up to an APFS-formatted Time Machine volume, you can’t even access the backups from a Mac with Catalina or an earlier macOS version installed. This might go without saying, but I know enough people with mixed-system setups who will ask. I would set up any new Time Machine volume formatted with APFS, but not convert an old one from HFS+.īig Sur APFS-based Time Machine backups can’t be used in Catalina or earlier releases. While APFS has advantages for SSD-based storage, there really aren’t any for hard disk drives, the most likely kind of drive used for large-capacity backup drives. Because of the structural differences, you can’t just copy from HFS+ to APFS, either.
However, if you want to shift a drive from HFS+ to APFS, you have to reformat the drive, and that erases all the Time Machine backups. You can set up a drive from scratch with HFS+ to create new Time Machine volumes as well.
Your old HFS+ based Time Machine volumes remain valid and readable in Big Sur.
