If you're not using block-level backups to back up changes within files rather than the entire file every time it is changed, then there's only one backup type to schedule since the product backs up all changed files in their entirety every backup. If you're using block-level, then you want the product to back up changes within files (helpful for large files that change little day-to-day). In that case, you need to schedule a recurring full (e.g., once a week or once a month) so those files are backed up in their entirety. That's needed to manage retention. If you can imagine a large file that is backed up using block-level backups forever - we would be unable to delete old versions since every backup contains only part of the entire file.

Thanks David for your reply it has helped, thanks!

Are you able to clarify the retention policy if you have both Delete version older than and Keep number of version (for each file) enabled? Is a particular file that's been backed up evaluated against both policies and if one satisfies the criteria, then it moves onto the next file?

Using https://help.msp360.com/cloudberry-backup-mac-linux/backup/backup-types/file-level-backup#step6 as an example retention policy, say you have two files and a backup schedule configured to run once a month. One file, (FileA) changes every month while another (FileB) changes infrequently, say once a year (on the same day).

Does that mean after the 37th month's backup, FileA will only ever have 10 versions (the most recent 10 months) while FileB will only ever have 2 versions because by the time the backup runs (assume it has changed) the backup in the 1st year is already older than 1 year and so it's deleted? (And the 2nd year's version is kept because Always keep the last version is enabled?)

Is my understanding correct?

if you delete versions older than a time period, all the versions are removed when they age out, with the exception of the last version if you check the keep last version option. The number of versions you keep for each file is up to you and as long as they haven't aged out you'll have that many versions, assuming there have been that many changes and that many backups. If you decide you want to keep three versions, after the fourth version is backed up, the first version is removed. Also keep in mind that if you're doing block level backups you need to be aware that versions are going to be tied to the full backup of the file . So if you change your file every day and back it up every day and are running full backups once a month, you'll have 30 versions of that file that must be kept at a minimum before they can be removed because of the need to keep that full in order to restore the block-level file backups.

Ok great, many thanks for clarifying that too.