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What Do I Do When Time Machine Reports It Is Full?

I have a 10TB external hard drive and today Time machine is reporting an error that the disk does not have enough room for the next backup. I thought that Time machine automatically deleted older backups to make way for the latest. Am I correct, is something wrong or do I need to do something to correct this?
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Ian Oultram

Comments: 9 Responses to “What Do I Do When Time Machine Reports It Is Full?”

    8 months ago

    Time Machine does delete older versions of files, yes. But it will keep the last version of a file around. For instance, say you create a file and over the course of a month you change it 9 times. It will have 10 versions of the file then. Then you delete the file. Now you have 10 versions of the file, the original and 9 others including the last one before it was deleted, right? Eventually is culls the first 9 versions and just has the final one. But it won't delete the file one.

    A backup wouldn't be worth much if it just deleted files forever and completely without a way to get back at least one version.

    Repeat that a bunch of times and that's how a Time Machine backup will fill up.

    You never mention how much data you have and how you use your Mac, but for some people this will take many many years to happen. But for others it will happen in a shorter time as they create lots of large files (video projects, perhaps?) and delete or archive them very quickly.

    You can erase the backup drive and start again, or get a larger backup drive and start a new one. Hard to advise which one is right for you since I don't know more about your situation. I also don't know how old this Time Machine backup is, whether it is 6 months or 6 years.

    One technique to make a Time Machine drive last longer is to use the Time Machine options to exclude folders that really don't need backing up. Sometimes these are large files that are created and deleted often. For instance, if you are using a third-party video, graphics or audio editor it may have a folder where it creates and deletes "render files" constantly. Time Machine already excludes standard caches, but not all apps handle cache files that way.

    Ian Oultram
    8 months ago

    Hi Gary, I can sort of make sense of what you are saying. This drive has been in use for TM since April last year. I can go back in TM to last September. I have a 500gb SSD in my iMac. which has 168 gb free. I have excluded all non-essential files.

    I work a lot with large Keynote presentations (1.5+ gb) plus large Pages and Affinity Publisher files. I make a lot of changes to these on a regular basis.

    So am I OK to just delete the older backup files in TM to clear some space?

    Ian Oultram
    8 months ago

    Just realised that TM was backing up two other external drives a 5tb and a 2tb, so I've now excluded these and TM seems a lot happier.

    Thanks Gary.

    8 months ago

    Ian: Don't try to micromanage your Time Machine backup by deleting older files. That could end in tears. Perhaps get a another drive (14 or 16TB) and start using that. When that fills up, erase the older drive and start using that one. Keep swapping on an annual basis when you run out of space.

    8 months ago

    Ian: Ah! Well, that would do it.

    Tom Gifford
    7 months ago

    Hi Ian - I just went through this. I decided to replace my old 8TB TM external drive with a 16TB drive. I found that Finder would not copy my old 8TB TM data to my new 16TB drive. After several days of "preparing" Finder began to copy and then failed - very frustrating. The only way I found to do it was to use SuperDuper! to do the copy. (Carbon Copy Cloner will not even attempt the copy.) Once I copied the old TM files to the new drive, I just told TM to use the new 16TB drive. All was then OK.

    Ian Oultram
    7 months ago

    Tom: Thanks for your input. I was wondering how to manage getting a larger drive, how would I access the files on my older TM drive, would I have to keep swapping it out when I wanted to access older backups? It may be me but it all seems a little unclear (and has done since my first Mac 20 years ago).

    7 months ago

    Ian: Hopefully you never need to access the older backups at all. The way it should go is you start a new backup on the new drive, set the old one aside, and then months later you erase and repurpose or recycle the old drive. You are just setting it aside in case of an emergency. Your comment "when I wanted to access older backups" seems to suggest you have to go into your Time Machine drive often to recover from mistakes. Is that right? That worries me. Using a backup to recover a file should be the safety net, not a normal everyday occurrence. But in an emergency you could plug in that old drive and access the file by entering Time Machine or just grabbing the file from it.

    Ian Oultram
    7 months ago

    Gary: Thanks for the additional info, I understand now.

    No, I don't regularly access TM only on odd occasions when I'm looking for an old version of a file or folder that I might have deleted.

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