#USING DISK IMAGE FOR BACKUP MAC FULL#
#USING DISK IMAGE FOR BACKUP MAC SERIES#

If you have an HFS+ Time Machine disk already set up and you want to continue using it with a Big Sur Mac, Big Sur will still use existing HFS+ Time Machine volumes without changing anything. As with Time Machine in older versions of macOS, though, files that don’t change between backups are only actually stored once to save disk space.

#USING DISK IMAGE FOR BACKUP MAC SERIES#

That said, because of how APFS works, you can always use Disk Utility to create non-Backup APFS volumes in the same container to backup multiple Macs to the same drive or use the drive’s free space for other things.īackups in Big Sur no longer take the form of endless nested folders, but of a series of APFS snapshots that each look like their own distinct volume. It’s used for Time Machine backups and nothing else, and you can’t back more than one Mac up to the same APFS volume (you get an error message if you try). And once you’ve designated a disk as a Backup volume, you can’t do anything else with it.

Unless you’re backing up to a network drive or continuing to use an HFS+ Time Machine configuration that you set up in a previous version of macOS, Time Machine will only backup to one of these special APFS volumes.

According to The Eclectic Light Company’s Howard Oakley, who has taken it upon himself to describe Apple’s APFS changes in Big Sur in lieu of an official deep dive, Apple has added a new APFS volume role called “Backup” specifically for Time Machine backup volumes. That changes in Big Sur, at least when you set up a new Time Machine volume. If there’s space left on the HFS+ volume that’s not being used by backups, you’re free to use it for other things.

#USING DISK IMAGE FOR BACKUP MAC FULL#

Time Machine creates a Backups.backupdb folder on the drive, and inside of that folder is a bunch of other folders: one each for each Mac you’re backing up to that drive, and then within those, one for every discrete backup each Mac has made.Įach of those backup folders appears to contain a full collection of every single file on your disk at the time, though in reality files that didn’t change between backups are hard linked so that you’re not wasting tons of space storing the same file over and over. In Catalina, you select an external volume connected via Thunderbolt or USB to use with Time Machine, and the partition is reformatted as an HFS+ volume whether you encrypt it or not is up to you. Further Reading A ZFS developer’s analysis of the good and bad in Apple’s new APFS file system

Using disk image for backup mac