CCC and Time Machine are both capable of creating snapshots on a given APFS volume. The snapshots that are created by each are exactly comparable – there's no technical difference between a snapshot created by CCC vs. a snapshot created by Time Machine. If you enable Time Machine and you do not specifically exclude your CCC source or backup volume from Time Machine's purview, Time Machine will automatically create and delete its own snapshots on those volumes. CCC is ambivalent about the snapshots that it presents for restoring, so it is acceptable to allow Time Machine to create snapshots on your CCC source and destination volumes.
However, you should carefully consider whether you want to allow both CCC and Time Machine to create snapshots on any given volume. Redundant snapshots managed by different retention policies is not harmful, but will probably result in a less effective retention schedule. Time Machine only retains snapshots for 24 hours, though, so the concern is only applicable to one day's worth of snapshots.
Disabling Time Machine snapshots for an individual volume
Many users find that snapshots are still created on a volume even after disabling snapshot support within CCC for that volume. Disabling snapshot support only affects CCC's creation and removal of snapshots from that volume, it does not affect Time Machine. CCC's snapshot list will indicate the icon of the application that created the snapshot:
Snapshot created by CCC
Snapshot created by Time Machine
If you would like to prevent Time Machine from creating snapshots on a given volume, you can exclude that volume from Time Machine:
- Open the System Settings application and click General in the sidebar
- Open the Time Machine panel
- Click on the Options... button
- Click the + button and select the volume you would like to exclude