When you configure a backup on a locally-attached backup disk, CCC will recommend that you enable backup versioning by default. When backup versioning ("CCC Snapshots") is enabled, those versions of your backups will consume some amount of space, and that will add up to more disk usage than what you have on the source. Eventually that disk usage can consume most of the free space on your backup disk. Do not be alarmed by this, this is normal – CCC will automatically manage the free space on your backup volume.
My backup disk is nearly full. Should I get a larger backup disk?
In most cases, no – you don't need to get a larger backup disk. If your backup disk has a substantively larger capacity than the disk usage of the source, then CCC will be able to manage the free space on the backup disk just fine. By default, CCC will delete the oldest backups when free space is less than 30GB. If CCC needs more than that to complete a backup, it will remove additional backup versions to make more free space available. Again, this is completely automated, you don't have to intervene to make more space available.
There are some cases, though, where you may want to consider getting a larger backup disk. For example, suppose you have a 1TB backup disk and 850GB of data on your startup disk. This leaves just 150GB of free space overhead on the destination – space that must be shared between backup versioning and making a safe update to the backup. If you have really large files in your data set (e.g. virtual machine files), this may not be enough free space. With any data set, though, 150GB may not be enough space for a long retention of backup versions.
You may also prefer to get a larger backup disk if you want to use storage space on the backup disk for things other than your CCC backup. If this describes your situation, there are two important details to bear in mind:
- You should dedicate a volume on your backup disk specifically to your CCC backup task. CCC backups are non-proprietary, so having a dedicated backup volume is the only way we can guarantee that you will be able to restore the source back to its original state.
- You can fine-tune how much space backup versions are allowed to consume by setting a custom Snapshot Retention Policy for your CCC backup volume.
You can learn more about these topics from the resources listed below.
OK, I do need a larger backup disk. Can I migrate my existing backup to the new disk? Should I create a new backup task?
Backup versions cannot be migrated to a different disk, and generally you should establish your new backup using the original source volume as the source to the task (not the old backup disk). If you're replacing your backup disk, use the same CCC backup task – click on the Destination selector and choose Choose a different destination. If you're adding a new backup disk, create a new task for the new source:destination setup.