![]() ![]() From articles I've seen online it appears that early versions of High Sierra treated snapshots as used space in System Information, but I don't have a High Sierra system handy on which to check if this still applies as late as macOS 10.13.6. System Information in Mojave and later reports free space in the same way as Finder. You can see the actual free space (not including the snapshots) by using the "df -h /" command in Terminal (-h gives human readable output rather than block counts note that it reports power-of-two mega/giga/terabytes whereas Finder uses power-of-ten to convert the df numbers to Finder equivalents, add 4% for megabytes, 7% for gigabytes or 10% for terabytes). Other old snapshots are deleted first in the hope that will free up enough space.īecause snapshots get deleted automatically, the free space reported by Finder includes the total size of the snapshots, which are actually used space according to the file system. MacOS automatically deletes old snapshots as disk space starts to get low, with a priority system: reference snapshots for external backups are retained as long as possible, because if they get deleted, the next backup may require a deep scan of the entire volume, resulting in a much slower backup. To get that free space back, all snapshots containing that file also need to be deleted. If you delete a file, the disk space occupied by that file is not freed if there is an existing snapshot in which that file existed. Old snapshots (for local or external backups) are retained on the source drive as long as there is plenty of free disk space, to extend the utility of local snapshots and to allow restoring recent backups even if the backup drive is not connected, or to allow rolling the system back to a recent state (a new feature in Catalina).ĪPFS snapshots retain the state of the entire volume at a point in time.Local snapshots are created when a backup drive is not available at the regular backup time, to give the user a chance to recover recently deleted or changed files.If you have configured Time Machine to use multiple backup drives, a reference snapshot is retained for each backup drive. After a backup is complete, the snapshot on the source drive is retained as a reference which gets used to work out differences for the next backup.That snapshot is used to copy files to the backup in a consistent state. A new APFS snapshot is created on the source drive when a backup is started. ![]() (Note that the term "snapshot" here has nothing to do with the VMware feature of the same name.)ĪPFS snapshots are used by Time Machine to support several features of the backup mechanism: I don't have anything I could try to import but that is likely to be running into the same issue. I can repeat similar "not enough space" errors from VMware Fusion if I attempt to clone an existing VM or create a VHD which is larger than the actual free space on the disk (as reported by df in Terminal, which is less than that reported by Finder). I have a probable explanation: Time Machine local snapshots on an APFS volume (High Sierra or later). ![]()
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