Time Machine Pruning

[JoelBC]

I received a notification that my Time Machine backup drive was full.

I looked at the Time Machine back up drive and noticed that Time Machine appears to do some pruning by retaining 1 backup per hour for the last 3 days, 1 backup per day for older days, 1 backup per week for even older days,...1 backup per month for the oldest days..

I was surprised when I got the notification that the Time Machine drive was full as I would have thought that Time Machine would have the "smarts" to prune the oldest backup to make room for the newer backups.

The two questions I have are:

1. Is it possible to configure Time Machine to prune the oldest backups to make room for the newer backups so that the user never gets the message that the Time Machine backup drive is full. If yes, then how?

2. Why does Time Machine not have this "auto pruning" capability? What was Apple thinking?

Thanks.

Joel

 

[kitKAC]

1. It does.

2. It does.

 

[JoelBC]

@kitKAC, appreciated.

The question therefore is why did I get a message that my Time Machine drive was full (and further backups could to be made)?

 

[HobeSoundDarryl]

Generally, that shouldn't happen. However, I think I recall this scenario when the Time Machine disc is not about 3X or more larger than the total capacity being backed up. Do you perhaps have something like X GBs to backup and are trying to do so to a (near) same-size drive allocated as TM? If so, replace the TM drive with one several times larger and it will likely avoid this issue when it fills (by auto-deleting the oldest copies when it needs new space).

Another scenario I also think I recall is when the Mac disc is nearly full. If Mac is almost full, TM can become "full" too (even if seemingly illogical because they are separate discs).

And still another: BIG files in duplicate take up a lot of TM room and NEED a lot of room for new backups. If you have very large files (maybe video files) that you tweak, a near full TM may not quite have the free space for that size files. It may want to backup first BEFORE deleting what may be the ONLY other (prior) copy in the archive so you are not temporarily naked (without any backup at all). Again, this is where having a multiple of total space to be backed up comes into play.

I'm not 100% sure I'm remembering those right... but I'm about 80% confident that THAT first or second one can be the trigger for TM "disk full" and #3 is only towards about 50% (something I think I read somewhere).

Inspired by the genius of Siri , I just took a quick look at "here's what I found on the web for time machine full" and there are other possibilities including a corrupt backup (just erase and start a new backup), TM bugs that sometimes result in this, etc. So if neither of the above applies, the solution may be to wipe the TM backup drive and then select it as a "new" TM backup drive and let TM create a new backup to it. This will take a LONG time but it may reset/fix whatever caused the current backup to stop deleting the oldest files so it is possible to fill up.

 

[JoelBC]

@HobeSoundDarryl Appreciate teh response. I have a 1 TB SSD in my MBP that is backing up to a 8 TB SSD so size should not be a problem.

I appreciate you looking voting I will continue to do teh same but will likely call Apple should the problem keep happening!

 

[HobeSoundDarryl]

In that quick look-around, I did see someone posting about small Mac drive backing up to 10TB and getting this message. And I believe that remedy was erase the disc and start a new TM backup (implying a corrupted TM backup, not properly deleting the oldest stuff to make room for new).

I skimmed through recent history and found this (also 10TB TM drive) reference which implies just an outright BUG in TM: https://discussions.apple.com/thread/252529408 with no remedy.

My primary is the TM tool on a Synology NAS but I also backup to TWO DAS drives (one kept offsite regularly rotating with the other) and never having a problem with any of these three. All are HDDs but that shouldn't have anything to do with it.

Unless someone comes up with something to help you- or Apple does- I'd probably just reformat the 8TB and start a new TM backup from scratch. You'll lose all that history but the clean start will likely fix any potential bug in that backup that was preventing old files from being cleared out for new backups.

If that history is important to you, buy an 8TB or larger HDD for cheap, copy the entire contents of the SSD to the HDD and then reformat it and reallocate it as TM drive. Then, you would still have a way to get to any old backup on the HDD if needed while starting a brand new TM archive on the SSD.

 

[JoelBC]

@HobeSoundDarryl : I greatly appreciate the help. Thank you!

 

[ignatius345]

Unless someone comes up with something to help you- or Apple does- I'd probably just reformat the 8TB and start a new TM backup from scratch. You'll lose all that history but the clean start will likely fix any potential bug in that backup that was preventing old files from being cleared out for new backups.

Another good reason to set it up fresh -- if this Time Machine drive was set up very long ago, it could be running on the old HFS+ version of Time Machine, which is slower and more error-prone, from what I understand. Even on newer macOS versions, Time Machine will continue to make HFS+ backups to a drive that has already been set up that way -- but when setting up a new Time Machine drive, it will use the much better APFS snapshot-based version.

Eclectic Light Company has some very deep dives on the subject.

 

[JoelBC]

@ignatius345: I thank you for taking the time to help as well as providing the link.

The drive I am using is approximately 6 months old and is APFS formatted so that is not the issue.

Will continue to hunt for an answer.

Thank you.

 

[JoelBC]

I called Apple Support earlier today and explained the problem to them. Apple Support had no explanation as to why the pruning failed or how to make sure it would work in the future.

The advice was to delete older backspaces and, should the problem reoccur, call them back.

While not surprised, it was not the response I was hoping for.

 

[ndouglas]

I freed up 190 gb on a 2tb drive last night thinking that should be enough for backing up a new computer with Time Machine. It seems it is not enough as I got that similar message, the drive is full so the new computer can’t even do one initial backup. I am doing my own manual “pruning” which takes a LONG time … to try to pare down the backup folder used by Time Machine. Overall, a frustrating process.

Sorry to hear OP got no help from Apple Support. I usually feel worse any time I contact them too, due to similar no/little help and the amount of time on the phone wasted.

Overall I think I understand the idea of Time Machine and its usefulness, for the scenario of one folder, one file, or set of files that I want to locate… however that scenario has never occurred (that I recall) in my 15+ years of using it. So, I’m debating now whether I want to keep using it. It seems my old fashioned way of backing up has been the best for my needs, that is, separate from Time Machine to just have a set of folders that I copy to an external drive, for various documents that I want to save.

 

[JoelBC]

Overall I think I understand the idea of Time Machine and its usefulness, for the scenario of one folder, one file, or set of files that I want to locate… however that scenario has never occurred (that I recall) in my 15+ years of using it. So, I’m debating now whether I want to keep using it. It seems my old fashioned way of backing up has been the best for my needs, that is, separate from Time Machine to just have a set of folders that I copy to an external drive, for various documents that I want to save.

The advantage of TimeMachine is that its backups can be used with migration assistant if there is ever a need to install / reinstall from scratch. While I have never had a complete system failure I have used this feature once (when I did something really stupid) and it saved me. Wold not have been possible with simply backing up my documents folder, etc.

 

[HDFan]

It seems my old fashioned way of backing up has been the best for my needs, that is, separate from Time Machine to just have a set of folders that I copy to an external drive, for various documents that I want to save.

The thing that time machine provides (when it works) is automatic versioning. It only backs up changed files and will keep older versions as long as you have disk space. That is difficult to duplicate when copying folders to an external drive.