Today’s Question: I have Time Machine backups dating back to 2020. I am sure the backups are taking up disk space. What is your recommendation for how many backups should be kept? What is the best method for deleting the old backups?
Tim’s Quick Answer: I do not recommend attempting to delete old backups with Time Machine. The backups are incremental, and Time Machine will automatically (and safely) delete old backups when the drive starts to get full.
More Detail: Time Machine is the backup application included with the MacOS operating system. It is an incremental backup application that preserves versions of files over time as space allows. This can be tremendously helpful for recovering files that were deleted accidentally, recovering an older version of a file from before a problem occurred, or even restoring to a new computer based on the backup of a previous computer.
Time Machine creates and preserves backups based on space being available on the hard drive being used for the backup. Those backups are created hourly for the past 24 hours, daily for the past month, and weekly going back as far in time as storage space on the drive allows.
I recommend using a dedicated hard drive for each Time Machine backup, with a drive that has about double the storage capacity of the drive being backed up. That way there’s no need to be concerned about old backups taking up space, because the entire drive is dedicated to the backup task.
When the hard drive starts to get full, Time Machine will automatically remove older backups. All files that are currently on the hard drive will be retained on the backup drive, but older versions of files that are represented by a more recent backup will be discarded to recover storage space.
In other words, as the drive fills you will lose the ability to go back in time to the oldest versions of files because those older backups will have been discarded. However, you will still retain a current backup of all files as they are on the hard drive. The bottom line is that if you’re using a dedicated hard drive for a Time Machine backup you don’t need to clear out old backups. You just need to make sure the drive is connected on a regular basis so the backup can be updated.