Hi - I have close to 3 TB of free space on my back up drive that time machine is not using. Is there some way to get time machine know the know what free space is available, and to adjust when to clean old files accordingly? I know this cannot be done use system preferences, but may there is a way using the CLI? Thanks for any assist I can get on this. I have os x 12.4
MacBook Pro 16″, macOS 12.4
The problem with using the CLI to try to tweak things like Time Machine is that those changes can backfire when the MacOS is updated. It is another thing one will have to keep track of, but when a MacOS update is done often (sometimes) these parameters are reset back to defaults. That could result in unexpected behaviors or results.
As leroydouglas pointed out, the MacOS keeps weekly backups until the drive fills up. Hourly and daily as indicated. The only reason your drive has not filled up is that your weekly backups haven't extended back in time long enough, but eventually it will.
In fact, you do not want to accelerate the filling up of the backup drive. The performance (speed) of the backups degrades significantly as the drive gets closer to full. Time Machine has to work more to figure out which older backups to remove and how to keep newer ones. These backups are not separate blocks on the drive, they reference unchanged and changed files differently, through soft links, it's actually quite complex, everything is interconnected, like a mass of tangled spaghetti. It works well (anyone who has restored files or migrated to new systems can attest to that) but as the drive fills up, Time Machine gets slower and slower as it has less and less room to work within. If the backup drive is a mechanical (spinning) drive formatted as APFS, as is typical for Time Machine under Monterey, that can be VERY slow (see
https://bombich.com/blog/2019/09/12/analysis-apfs-enumeration-performance-on-rotational-hard-drives )
Eventually (this may take a long time, but sometimes not), the drive may get so full that Time Machine cannot proceed further and a new drive must be started. But as the drive gets close to full, incremental backups that used to take seconds or minutes can take many minutes or even longer. One symptom of this is that the "cleaning up" phase at the end of the backup takes longer and longer.
The problem with using the CLI to try to tweak things like Time Machine is that those changes can backfire when the MacOS is updated. It is another thing one will have to keep track of, but when a MacOS update is done often (sometimes) these parameters are reset back to defaults. That could result in unexpected behaviors or results.
As leroydouglas pointed out, the MacOS keeps weekly backups until the drive fills up. Hourly and daily as indicated. The only reason your drive has not filled up is that your weekly backups haven't extended back in time long enough, but eventually it will.
In fact, you do not want to accelerate the filling up of the backup drive. The performance (speed) of the backups degrades significantly as the drive gets closer to full. Time Machine has to work more to figure out which older backups to remove and how to keep newer ones. These backups are not separate blocks on the drive, they reference unchanged and changed files differently, through soft links, it's actually quite complex, everything is interconnected, like a mass of tangled spaghetti. It works well (anyone who has restored files or migrated to new systems can attest to that) but as the drive fills up, Time Machine gets slower and slower as it has less and less room to work within. If the backup drive is a mechanical (spinning) drive formatted as APFS, as is typical for Time Machine under Monterey, that can be VERY slow (see
https://bombich.com/blog/2019/09/12/analysis-apfs-enumeration-performance-on-rotational-hard-drives )
Eventually (this may take a long time, but sometimes not), the drive may get so full that Time Machine cannot proceed further and a new drive must be started. But as the drive gets close to full, incremental backups that used to take seconds or minutes can take many minutes or even longer. One symptom of this is that the "cleaning up" phase at the end of the backup takes longer and longer.
Does it tell you it has run out of space and will delete older backups? If not, then it will use the extra 3TB when it needs it.
Time Machine does not duplicate files that have not changed. If you haven't changed a file, it will just reference the original file and never make another copy. A Time Machine backup won't continually grow unless you continually edit old files or add new files.
Also, Time Machine is not an archival backup. That means anything you delete from your Mac could be deleted from the backup, eventually. It shouldn't be deleted until it runs out of space.
Dexter5772 wrote:
Hi - I have close to 3 TB of free space on my back up drive that time machine is not using. Is there some way to get time machine know the know what free space is available, and to adjust when to clean old files accordingly? I know this cannot be done use system preferences, but may there is a way using the CLI? Thanks for any assist I can get on this. I have os x 12.4
CLI...(?) ...command line interface? I would not recommend the Terminal app to try and manipulate TM drive.
TM likes to have its own dedicated drive.. no partitions, no extra containers, no manually added data.
The go to way to get beyond issues, would be to erase reformat the parent drive and start a new— there is no reason why the full 3TB can not be utilized unless you have corrupted the database.
Erase and reformat a storage device in Disk Utility on Mac
Erase and reformat a storage device in Disk Utility on Mac - Apple Support
if you value your user data—
3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.
How to Get Time Machine to Keep More History with a Large Backup Drive
