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Product Tour: Learn how to customize the retention of backup history on your backup
CCC will "thin out" snapshots at the beginning of the backup task to reduce overall snapshot disk usage while retaining a broad age range of backup versions. After thinning, CCC will then prune the oldest snapshots if free space is below a threshold. By default, CCC will apply the following retention settings:
- Hourly snapshots will be retained for 24 hours
- Daily snapshots will be retained for 30 days
- Weekly snapshots will be retained indefinitely
- SafetyNet snapshots will be retained for 7 days
- [Pruning] The oldest snapshots will be deleted when free space is less than 30GB, regardless of the thinning settings noted above.
Customizing the retention policy
The default retention settings work well for a simple one-source, dedicated-backup configuration. These settings provide a good balance between version granularity, max retention age, and snapshot disk usage. If your backup requirements are more complex, you can define a custom snapshot retention policy. With a custom policy you could choose to retain hourly snapshots indefinitely (at one extreme), or choose to remove snapshots that are older than a specific number of days, or apply a specific free space or snapshot disk usage requirement so that snapshot disk usage can be balanced more fairly among multiple backup volumes on the same disk.
Select a volume in CCC's sidebar, then click the Customize button in the lower-right corner of the window to customize the snapshot retention policy for that volume. Click Use defaults to return to the default settings.
CCC Product Tour: Show me how to customize the snapshot retention policy for my backup volume
The Snapshot Pruning settings are optional when using a customized retention policy. If you don't want CCC to delete snapshots when the disk fills up, you can disable the Minimum free space setting. Note that your backup tasks will fail with an error if the destination runs out of space and CCC is not allowed to remove snapshots. You can also configure CCC's Dashboard to send notifications about snapshot pruning to the macOS Notification Center.
Snapshots created by other applications
During snapshot thinning and pruning, CCC will never delete snapshots created by other applications. If you would like to remove snapshots created by another application, select the relevant volume in CCC's sidebar, select the snapshots you would like to remove, then press the Delete key.
CCC's snapshot retention policy is only applied when snapshots are enabled for that volume
If you disable CCC snapshot support for a volume that contains previously-created CCC snapshots, CCC will not perform automated snapshot thinning on that volume. When you disable snapshot support, you are welcome to delete the snapshots listed above the snapshot toggle button. Simply select one or more snapshots listed in the table, then press the Delete key.
The snapshot retention policy defines which snapshots will be retained, not when they will be created
CCC creates snapshots when your backup tasks run, and only when your backup tasks run. CCC will never create snapshots outside of a scheduled or manually-run backup task. As such, a retention policy that saves "up to one snapshot per hour for 24 hours" does not imply that you will have 24 snapshots for the last day. If you have a backup task configured to run only on a daily basis, you should expect to see only one snapshot on the volume. If you want to have hourly snapshots, be sure to configure your backup task to run on an hourly basis.
CCC will override your free space limit if that's required to complete a backup
The default free space limit of 30GB will generally ensure that CCC can write 30GB of data to your destination volume during each backup task. If CCC finds more than 30GB of data to copy and runs out of room on the destination, and only when the Minimum free space setting is enabled, CCC will remove additional snapshots during the backup task to free additional space. When this "emergency" thinning takes place, CCC will add a notification to your backup task event (in the Task History window), suggesting that you review the Snapshot Retention Policy for your destination volume.
To review the Snapshot Retention Policy: Click on the destination volume in CCC's sidebar, then click on the Customize button to customize the retention policy settings. The specific setting that you should consider changing is the one labeled "Minimum free space xx GB". When reviewing the free space limit, consider whether your backup tasks generally copy more than 30GB (you can make that assessment in CCC's Task History window). Specify a value that will leave enough space to accommodate the amount of data that usually gets copied to the destination to avoid the emergency thinning and associated notification.
If you notice that your backup task is suddenly copying a lot more data than usual, please take a moment to look for potential problems. For example, if you have more than one backup task backing up different sources to the same destination, those tasks may be conflicting, removing each others' files. You should also determine if disk usage on the destination is unusually high compared to the source (excluding snapshot disk usage). If the disk usage looks suspicious, or if the amount of data that CCC is copying is difficult to explain, please don't hesitate to contact us for an additional review of your setup.
Protected Snapshots
At times you may want to create a snapshot manually, or preserve a particular snapshot independently of the Snapshot Retention Policy. CCC Protected Snapshots provide that functionality. Protected snapshots are spared during automated snapshot thinning and pruning activity, e.g. at the beginning of a backup task, and whenever free space gets too low during a backup task. Note that snapshot protection does not prevent you from manually deleting a snapshot, nor can it protect the snapshot from being deleted by other applications.
To create a new protected snapshot on a volume, select that volume in CCC's sidebar, then right-click on the Snapshots table and choose Create protected snapshot from the contextual menu. To mark an existing snapshot as protected, right-click on that snapshot, then select Protect Snapshot…. CCC will present a dialog that gives you the opportunity to specify an optional comment while protecting the snapshot.
To view the comment later, hover your mouse over the lock icon that identifies the snapshot as protected.