This is just a question about Time Machine and the backup hard drive

You may find the following article an interesting read to give you a bit more detail on how Time Machine works. Although it was written around macOS Sonoma, it is still relevant today with Sequoia.

• Time Machine in Sonoma: how we got here - The Eclectic Light Company

JigShaun1030 wrote:

I back up my iMac M1 daily. I suppose I can change that to weekly, I guess. I back up the whole system drive, which is a 1TB external Thunderbolt drive. I use a 5TB external USB drive to store the backups. I just checked, and on April 3rd, I purged all my backups (except the last couple) and started again. My understanding is that Time Machine only saves what has changed, right? I looked at the drive and it shows 18 backup files. They range in size from 450GB to 750 GB. I understand this to mean the size of the whole hard drive, right? Not the size of the changes. Yet, the drive reports there is only 1.45TB remaining. Even Disk Doctor reports I have used 3.5 TB of drive space. Clearly, the real size should be much smaller. Does Time Machine know the difference, or is it going to tell me there isn't enough space in only a couple of days?

Predicated on the 5 TB External Drive is dedicated to the sole and only purpose of using TM Backup

Having does this " I purged all my backups (except the last couple) and started again. "

However you managed to purged some TM Backup Snapshots is beyond understanding

Reason, TM Backup Utility Marks the Drive as Read Only

Having done what was done probably Corrupted the index file that TM Backup uses to keep track of changes and was in on the 5 TB Drive

It is suggested to Erase and reformat a storage device in Disk Utility on Mac using the instruction in that link

Then setup a the routine for this drive

Personally, I lean towards having redundancies

To truly protect your non replaceable Data

Have a 3-2-1 Rescue Plan in place and always current

3 Backups using 2 methods and 1 off site incase of natural disaster or un-natural disaster.

Each of the above should be done to a Dedicated Single Purposed External Drive 

Below link is intended to augment what TM Backup does 

https://bombich.com

JigShaun1030 wrote:

An observation: Time Machine is working on today's backup. It is 89% complete, and it reports it will not be done for another 20 minutes. It tells me it has copied 690 GB. I can assure you I haven't made over 700 GB of changes since yesterday. I admit it won't be a big deal if I have to erase this hard drive every two months and begin again. I'm just trying to make sure I understand what is going on here.

This is actually a new backup drive (not a new drive - but new for this purpose) and yes, strictly a TM drive. It was formatted before I started using it for TM. However, anything is possible. I've been using Apple Computers since the 1990s, but I don't claim to understand what's going on behind the scenes, so any or all of your observations could be correct. I think I'll follow your suggestion and go one further. I'm going to switch drives as well and see if maybe the hard drive could be contributing to the problem. It's never been used intensively, but it is at least 7 years old, if not older. Maybe failsafes aren't the best places to economize?

Thanks for your help.

Is the some Cloud Based Service active and used on this computer

In regards to the Size of each TM Backup

Some Cloud Based Services like iCloud and others like One Drive ( MS Windows ) or Google Drive could come into play here

I would really suggest you follow the advise from my colleague @ Tesserax

I think they is onto something there

" shared-pasteboard " specifically

~/Library/Group Containers/group.com.apple.coreservices.useractivityd/shared-pasteboard/archives/93E12DF7-A795-4F33-9AA3-649D0DFA8CBF

JigShaun1030 wrote:

I suggest starting by inspecting what those files could be. To do so, use this command in the Terminal app:

ls -lh ~/Library/Group\ Containers/group.com.apple.coreservices.useractivityd/shared-pasteboard/archives/

I tried this but Terminal returned Operation not permitted.

Since macOS Mojave and beyond (and even more locked down in macOS Sequoia), many parts of your ~/Library, especially things like Group Containers, are protected by System Integrity Protection (SIP) and the app-specific privacy permissions. Even ls won't work there without proper entitlements.

A couple of things you can try:

1. Use the same command, but this time start it with 'sudo'. This will elevate the command to the Administrator level, and you may need to enter your Administrator's account password when prompted.
2. Alternately, you can provide the Terminal app with Full Disk Access. I suggest you try the first option to see if you get the proper results.

I tried this one, and Terminal returned no matches found. Will it cause major problems if I simply move all the files into the trash? I know messing with anything in the Library can have damaging results. I'm going to reboot and try the Terminal commands again. Failing that, I'm thinking about starting up in safe mode. Maybe that will help? Whaddaya think?

You may not be able to do this as System files are typically controlled by SIP. SIP can be disabled, but is highly not recommended unless you really know what you are doing. Any mistakes could end up requiring that you re-install macOS. FYI ... booting up in Safe Mode does NOT disable SIP.

That folder is indeed used by Apple’s Handoff/Continuity features to support cross-device clipboard sharing. Typically, though, this is for transient, relatively small data: text snippets, small images, or maybe a copied file or two under a few hundred MB at most ...

... However, one likely culprit is that you may have accidentally copied a massive file or folder — possibly a disk image, virtual machine, or Final Cut project — and Handoff dutifully tried to sync it between devices.

I suggest starting by inspecting what those files could be. To do so, use this command in the Terminal app:

ls -lh ~/Library/Group\ Containers/group.com.apple.coreservices.useractivityd/shared-pasteboard/archives/

That should show you a list with sizes and timestamps. If they all appeared in a short time span, it likely points to a single event (like copying a huge folder).

If you’re confident you don’t need them (and frankly, 370 GB of old clipboard data is almost certainly not useful), go ahead and delete them with this command:

rm -rf ~/Library/Group\ Containers/group.com.apple.coreservices.useractivityd/shared-pasteboard/archives/*

Or move them to a temporary folder first if you want to double-check:

mkdir ~/Desktop/PasteboardBackup
mv ~/Library/Group\ Containers/group.com.apple.coreservices.useractivityd/shared-pasteboard/archives/* ~/Desktop/PasteboardBackup/

To help prevent recurrence, If you don’t use Universal Clipboard, consider disabling Handoff:

1. Go to System Settings > General > AirPlay & Handoff
2. Toggle off “Allow Handoff between this Mac and your iCloud devices”