Is it normal for my Time Machine drive to be filling up so fast?

[2024]

I have an M3 iMac with a 1TB internal SSD that is about half full. In early 2024 I started using a 2TB WD HDD for Time Machine (so about four times the data on the internal drive). In a year and a half the TM drive was so full that I couldn’t use it anymore. I bought a new 8TB WD HDD to replace it, thinking I'd get 5-6 years of TM backups out of it, but in only eight months it’s already over half full (5.2TB used).

Is this normal? I’m a light user; mostly Safari, Numbers, Pages, etc. Nothing more data-heavy than downloading the occasional song and taking a few photos and/or 1-2 minute videos now and then.

The TM drives were formatted by the iMac, so they’re APFS. I back up manually, twice a week, because I don’t feel the need to do it more often. I don’t understand how they can be filling up so fast. When I open the TM drive in Finder, it shows each semi-weekly backup as 500+ GB (in the Size column). However, that obviously can’t be each backup amount itself. I’ve excluded nothing from TM in Settings.

I’m very puzzled by all this. Does anyone have any thoughts?

When I add or move a photo, does the entire photos database get recreated in TM each time? My snapshots are removed after running TM, so I don't think they're somehow being backed up subsequently (if that's even possible).

I know about CCC and Super Duper, so they don’t need to plugged here. I want to know about my TM.

 

[FreakinEurekan]

Time Machine backs up what’s changed; if you add a photo it’s not going to re-backup the whole library but just that photo.

One data killer I’ve seen with Time Machine is “scratch” data, which can take a lot of forms but essentially it means data that’s only there temporarily. Sometimes it’s as simple as excluding your Downloads folder from the backup, though some apps (e.g. Adobe) will use a specific folder for scratch data and you should exclude that too.

Personally I recommend setting backup to Auto and either leave it on the Hourly setting, or Daily at the longest. You won’t really use much if any more disk space on TM and possibly less in the long run, because your backups will have better granularity and make it easier for TM to prune as necessary. And it’s an iMac, so there’s no reason to not just leave the TM drive connected full-time.

I know about CCC and Super Duper, so they don’t need to plugged here.

I hear ya… CCC and Super Duper are good apps but they are NOT BACKUPS. They are clones, which is a completely different (not invalid - but different) solution.

 

[Fishrrman]

"CCC and Super Duper are good apps but they are NOT BACKUPS. They are clones,"

This statement is ridiculous on its face.

From time to time, I've messed up a file, and needed to "get back to where I once belonged".

I reached for my CCC backup, found the file I needed, and things were working again.

I've also done this with entire accounts. It works. Running again, when (before) I wasn't.

A "clone" absolutely IS "a backup".
It's a backup of what your drive was like the moment you cloned it.
For me, that's about all I ever need.
And CCC can be set to retain changed versions of files, as well. It's callled "safety net".
Obviously you don't know what the app can do.

 

[BigBlur]

In a year and a half the TM drive was so full that I couldn’t use it anymore.

Did it give some sort of an error? It should start deleting the oldest backups.

Any chance you're using virtual machines? That is another thing that can take up a lot of space. If you've got a 100 GB virtual disk and make a small change inside the VM, it's going to backup the whole 100 GB virtual disk again unless you exclude it from the backup.

 

[!!!]

TM should automatically delete older backups to make room for new backups. You can delete individual backups as well.

I'd be more interested in finding out what's filling your drive so much. There used to be a free tool called TimeTracker, made by the same people as Pacifist. However it's no longer available and it only worked on HFS-formatted TM drives. BackupLoupe is a paid alternative, though I have not used it.

Some basic questions, though:
Do you use a virtual machine (VM)? They typically bloat TM backups due to the abstraction between the VM's FS and the underlying disk image.
Do you edit large movies?
Do you frequently move large files, or move or rename folders containing large files?
Do any of the websites you visit use local storage extensively?
Do you have any large apps that are frequently updated, particularly games?
Have you looked through your ~/Library folder? Anything stick out as particularly large? There may be a runaway app writing excessive amounts of data.

Other than that, there are some folders inside the hidden system /private/ directory that, for some reason, are backed up despite being caches or log files.

 

[svenmany]

My issue with TM was the spotlight indexes which got very, very large. I believe it is a bug and it forced me to stop using TM.

After my file changes were copied to the TM drive, Spotlight indexed everything, adding to whatever index was there before. All of that content was then put into an APFS snapshot on the TM drive. Those snapshots are what you see when you look at a TM drive in Finder. So each snapshot gets a spotlight index that is larger than the last. The bug I encountered related to just how large those indexes got. In fact, every time a TM drive was mounted, a reindexing of the oldest snapshot was done and the results added to the index in the root of the drive (which would make its way into the next snapshot). Since I reboot my computer regularly, this was a significant space hog and a constant wear on the drives.

To see if you are having this problem, you'll have to inspect the spotlight index using Terminal. Finder does not present the actual content of the drive's filesystem, only the snapshots there. You would also notice this problem if after a reboot, spotlight is very active for more than 10 minutes. For me, Spotlight would work for hours on the Time Machine volumes after every reboot.

 

[hobowankenobi]

TM should automatically delete older sets, so as a volume fills, it should not stop working, unless there is a problem or some file(s) are so large that even with the minimum versions kept (there is not enough free space to complete).

one of my gripes about TM has always been that there is not enough granular control. I would, for example, like to say that I want to keep 3 versions of some files, and only 1 of some, and perhaps 10 versions of others. All that is set automatically based on free space. More free space = more history.

One can consider excluding or limiting what is getting backed up too, to save space for more history of the most important/unique files.

Some will land on a more nuanced approach:

1. A snapshot or a full system clone on some predetermined schedule.
2. Continuous backup of important working files that change most often.

TM is pretty good for 2, but less useful for 1. Lots of other tools that can handle the system snapshot. With that in place (on another drive) TM could still do well with continuous backup of specific directories.