Time Machine - how to limit the space it uses in 10.15 on an external server USB disk

I know I could set up partitions, however would rather not do it that way, but can if needed.

That would be the way to do it. There is nothing in Time Machine to limit the size of the backup.

I don't thing HFS+ has any disk quota capability.

In the Advanced options under File Sharing for that drive, you can set it up as a Time Machine destination, and set a quota, but I don't think that can be done "per user" or "per source". I also don't know if the quota is designed to be per backup or total for all backups.

ChangeAgent wrote:

OK. I like to prevent TM filling the whole disk as I want to have space for other stuff.

Time Machine really wants its own dedicated drive. It is not advised to partition the external drive for both TM and as additional storage space. External drives are relatively inexpensive.

Time Machine is great when it works, however it is a bit finicky as it is. You will be setting yourself up for heart break down the line.

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.

Boot clone https://discussions.apple.com/docs/DOC-10081

How to use Time Machine to back up or restore your Mac: https://support.apple.com/en-us/HT201250

Use DiskUtility Restore feature https://support.apple.com/guide/disk-utility/restore-a-disk-dskutl14062/mac

note: >System Preferences>Security & Privacy >Privacy>Full Disk Access

unlock the padlock, press the + button and add Disk Utility

I was thinking about the desire to partition off the drive to control the size of the backup.

Based on many question here on how to move their backup to a new, larger drive, what do you plan on doing when you run out of space on the dedicated partition? You won't be able to expand the partition as you'll have one of the backup partitions directly after the first one. Unless you plan to put buffer partitions after the backup partitions, you'll have nowhere to expand into.

Get a drive that is sized appropriately for the two backups and leave it be.

Are you talking about quotas on a drive or quotas for Time Machine.

If someone thinks there is a way to do it in Time Machine, then there may be.

I have never had any desire to dig into the inner workings of Time Machine. I just turn it on and it works.

In the number of times I've looked into Time Machine problems, here, I don't remember anyone ever discussing disk quotas. However, I think limiting the space for a backup isn't useful, so I would likely have ignored anything like that.

dialabrain is 100% correct.

https://support.apple.com/guide/mac-help/types-of-disks-you-can-use-with-time-machine-mh15139/mac

For Time Machine to work, the file system it is writing to must support hard links to folders.

APFS does not support that feature. Most file systems do not. Apple added it to HFS+ for Time Machine.

I am fine with that as I do not need backups that go back

for years. If I have2+ months all is well. I have other systems in place that

go back further if needed. TM is just for the occasional by accident deleted

file etc. 

Then I would just buy a right-sized drive to backup the desired Macs for the time you need and leave it alone.

The bottom line is if you are trying to work around the design of Time Machine, it isn't the backup solution you should be using.