Time Machine backup is too large!

Hi!


I've opted to reformat my external hard drive (APFS) and initiate my Time Machine backups from scratch.


However, I've encountered an unusual issue: it appears to be miscalculating the amount it needs to back up.


Yesterday evening, I initiated the first Time Machine backup process. I'm using a 2 TB external hard drive, and my computer holds 660.76 GB of data. Strangely, after approximately 12 hours, it claimed there were still 8 hours left, and my external drive had only 60 TB of space remaining, suggesting it had copied 1940 GB, which doesn't make sense.


This morning, I decided to restart the process entirely.


And here we go again!


It now states that 4% is complete, with 149.19 GB copied. Again, this seems inconsistent.


If I have 660.76 GB to back up, then 4% of 660.76 equals 26.4304, not 149.19!


What could be causing this discrepancy?


Thanks!


MacBook Pro 16″

Posted on Dec 23, 2023 5:50 AM

Reply
8 replies

Dec 23, 2023 10:16 AM in response to leroydouglas

Because I would have gotten the error "Time Machine backup failed because there isn't enough space on your hard drive".


So I restarted my computer about 5 times, reformatted my external hard drive about 8 times, and then it worked. The calculations were perfect, and it took about 2 hours to complete.


Now, my external hard drive has 1.44 TB available, which makes total sense considering my computer had about 660 GB to backup.


All is now good.


However, there's something I've never seen before... Why are my backups sorted this way?



My backups have always been stored this way:



What is that about?


Thank you!

Dec 23, 2023 9:08 AM in response to Krissserz

Krissserz wrote:

Hi!

I've opted to reformat my external hard drive (APFS) and initiate my Time Machine backups from scratch.

However, I've encountered an unusual issue: it appears to be miscalculating the amount it needs to back up.

Yesterday evening, I initiated the first Time Machine backup process. I'm using a 2 TB external hard drive, and my computer holds 660.76 GB of data. Strangely, after approximately 12 hours, it claimed there were still 8 hours left, and my external drive had only 60 TB of space remaining, suggesting it had copied 1940 GB, which doesn't make sense.

This morning, I decided to restart the process entirely.

And here we go again!

It now states that 4% is complete, with 149.19 GB copied. Again, this seems inconsistent.

If I have 660.76 GB to back up, then 4% of 660.76 equals 26.4304, not 149.19!

What could be causing this discrepancy?

Thanks!


https://discussions.apple.com/content/attachment/f27eef84-3e1b-41aa-9987-cf4c0c642cd3
https://discussions.apple.com/content/attachment/34cdf648-02c9-4a0a-95c9-aabdbd10bea7


Why not let it finish...


then make some assessment of the situation.

Dec 23, 2023 11:16 AM in response to Krissserz

It sounds like Time Machine is now working ok for you.


I would also do the following:


(1) Try restoring one file or folder from Time Machine to make sure you can restore files.

(2) Consider adding a second Time Machine backup drive. Time Machine will try to alternate between them when you have more than one. If only one is mounted, it will use that one. Keep them both connected or if using a laptop, make sure to connect each one now every day or so to make sure each has an up to date backup.

(3) Consider adding a different type of backup, say a "cloning" program (SuperDuper, Carbon Copy Cloner and other programs can do this) which makes one copy of everything at the time of the backup. If done properly, the backup drive with these clones can even be booted from.


By adding different kinds and multiple backups, you are more resistant to a hardware failure of the backup media, or some other software issue that might interfere with restoring from a completed backup. Storing some subset of your very important files in the cloud adds another layer of protection (against theft, fire etc.).


Once you have your setup for backups done, you can just let them do their thing and be assured you are "covered."


This may sound a bit extreme but my experience is colored by my job where we do a lot of software and data analysis of data from spacecraft and redundancy in backups is mandatory. Also, eventually all hardware does fail. Because we keep computers running in our home until they actually do fail (I still have 2011 and 2013 MacBook Airs running, plus newer machines), we keep extra redundancy in backups. When the computer does fail, transfer to a new computer is very easy with these backups.


An example of why redundant backups are important might be a power surge that damages both the computer and the backup disk connected to it. Having other backups not connected protects against that.

Dec 23, 2023 11:06 AM in response to Krissserz

Krissserz wrote:

All is now good.

However, there's something I've never seen before... Why are my backups sorted this way?


Things are always changing Krissserz ...


new macOS, new file system, new look.



Stay current along the way and all these little things will seem less of a concern.


The current stable release of Sonoma including bug fixes,  security updates  is macOS 14.2.1

Keep your Mac up to date - Apple Support

Keep your Mac up to date - Apple Support


Dec 23, 2023 5:38 PM in response to Krissserz

Can someone please explain to me how Time Machine backups work?


My computer has 665.49 GB of data:



My external hard drive has 2 TB of capacity:



So why am I getting this message?



Inside my External hard drive, there's this:



And each backup is about 565 GB:



This NEVER happened to me before... I've been using Time Machine for my backups for a decade. Today, I decided to start fresh, and I'm getting all of those problems.


Can someone please tell me what's going on?


Thank you!

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Time Machine backup is too large!

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