Time Machine over the network says it's out of space?

I got a new M1 Macbook Air, so my old MBP is being repurposed as a home server. I shared the Time Machine drive over the network so the new Air can back up without plugging & unplugging, but this morning I get a “Time Machine couldn’t complete the backup” message, apparently because the TM drive is full.

The only thing on this drive are time machine backups, and at 5TB it should be big enough. The Home Server machine appears to have inherited the MPB’s backup history despite a complete wipe, (maybe because of a hardware ID or something). Shouldn’t TM have deleted some of the old backups from the Home Server to make space for the incoming backups from the new Air?

What should be my next step to get this working? I guess I could just format the drive and start fresh, but it feels like I shouldn’t have to.

Since the MBA is a new machine, and TimeMachine doesn’t know it’s an upgrade from the MBP, it is most likely treating them as different machines, and thus it wouldn’t delete some of the other machine’s backups to make room for this machine’s backups.

If it’s still set up in the MBP, you could delete old backups, or as you said, format the drive.

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Because Apple is apparently satisfied with how Time Machine works, it has never really gotten the attention it needs for anything but the most basic setup.

Time Machine and Time Capsule is really best when there’s one Mac backing up to one drive/partition.

The best way to handle a change like this is to completely reformat the drive and start fresh.

If you want to share one shared/network drive with various computers, I recommend Arq.

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It is treating them as different machines. The MBP has been reformatted and set up as the home server, but appears to have inherited its old backup history in Time Machine, so I can go in and delete old backups, maybe I’ll do that.

As @tjluoma says, it seems that Time Machine really works best if there’s one drive per backup. Ideally, (IMO at least), the Time Machine disk would be managed in a way that old backups of one computer could be deleted to make space for new backups of a new computer.

I disagree with this. I know a lot of people say this, but I think it’s folklore.
The backups are stored in a sparse bundle for each machine, so there should be no problem with more than one machine using a backup destination.

Having said that, Time Machine hasn’t been reliable for me at all. It’s fine for maybe 6 months, then loses its mind and wants you to start over. This comes up every so often here on the forum. This may be the source of the myth that you can only use one machine per drive / partition.

Arq 5 has been very reliable for me. Arq 6 was a disaster (that I fortunately skipped), and I’m leery of moving to Arq 7 because of that. So I would say Arq 5 or Carbon Copy Cloner would be good bets for backup software.

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@JohnBeales also. I backup four computers to a Synology NAS file server. As described in the Synology KB on how to setup, we use a special login ID for each device. Each is seperate and distinct from their normal login because for the TimeMachine backup we put a quota on file space, which TimeMachine respects as it would if it were a USB device with a specific amount of space. Works just fine. Probably a way to do this on @JohnBeales Home Server.

You’re welcome to believe what you want, but it is the actual lived experience of many people, including myself… and, as we learned, yours as well:

First, you say it’s a “myth” that it does not work, but then you also agree that it does not work. :thinking:

I would counter by saying that the idea that you can (reliably!) use Time Capsule with many different Macs is the actual myth or a legend/

Apple clearly intended it to work that way, but in actual practice, it does not work well.

That doesn’t mean it works never but if anyone actually had it work for them, I would consider them the exception, rather than the rule.

Heck, I have even had Time Machine tell me that it ran out of space on a drive solely dedicated to the same machine.

I had the same experience with Arq 5 vs 6, but 7 has been completely reliable, and I would not hesitate to recommend it.

In other words:

  • multiple backups to a single device is no worse than a single backup
  • either way, eventually TimeMachine will fail

Haha. I’ve always just used it with USB and it’s never failed. We’ll see if my new, more complicated, setup fails :wink:

I have found that backups are very slow to use, and setting up a new mac from a TM disk takes forever. A Carbon Copy Cloner clone is handiest for that, but my multiple layers of backup include Time Machine.


Can relate.
I just eliminated Borg backup and Vorta from my stable of backup routines. (But because I added CCC and Arq backups to my new TrueNAS Core VM running on a used Dell server I bought, and using the zfs file system which is really robust.)