What do you do when Time Capsule runs out of room?

Basically yes.. an Erase is required.

Although in theory Time Machine should be able to delete old files so there is always sufficient space.. the reality since Apple started cranking out a new Mac OS annually is Time Machine can no longer delete enough to make significant differences.. with all those files piled on top of each other.

It tends to become much slower and less efficient as well.

However you can archive the TC before you erase to preserve the current backup.. plug a 2TB or larger USB drive into the TC and run archive function.. it will take more than a day normally as USB on the TC is slow.

Once backed up you can then erase and start over with fresh clean backup. If you ever need earlier files you can plug the USB into the computer and access the files directly.

NOTE.. it is also possible to plug a larger USB drive into the TC.. and use that for target.. you will still need to start a new backup.. however I don't recommend it as USB is slow and much more problematic than using the internal disk.

If the old backups are important to you, use the Archive function in AirPort Utility to copy over everything on the Time Capsule drive to an attached USB drive.

Then, erase the Time Capsule drive and start over with a new backup and move forward

Chances are, after a month or two, you will decide that you really don't need the old backups from months and maybe years back and you can erase the USB drive and use it as a spare. Or, set up backups to both the Time Capsule and the USB drive using Time Machine and/or Carbon Copy Cloner.

If the old backups are not that important to you......(all that most of us really need is a current backup of a Mac, in case the drive crashes on the Mac).....then you can simply erase the Time Capsule drive and start over again.

Time Machine usually assumes management of the entire device or entire partition, and will fill it with backup data, and will then purge the oldest backup data as necessary and as new backups are performed. Let Time Machine run. It’ll manage what’s necessary here.

This is correct in theory, but Apple does not tell you that Time Machine has problems when the backup drive is close to full and the new backup to be performed is larger than normal.....after an operating system update, or a lot of new data has been added since the last backup.

When this occurs, a message will be displayed that indicates that there is not enough space on the backup drive for the backup to occur. What is really happening is that Time Machine cannot delete enough old files to make room for the new larger than normal backup.

Pondini explained all of this in his Time Machine Troubleshooting document. Apple never explained this to users though.

Users often want to know how this stuff works, after all.

And how it doesn't.

A 10 second forum search finds well over 3,000 posts from users wanting to know why......when the Time Capsule is full, Time Machine is not deleting old backups to allow a new backup to occur.

Bottom line......I don't trust Time Machine to take care of things when the drive is full or close to full, and I advise users to do the same. Your advice may be different.

You might well be correct in the intent of the question, but that’s not what the literal question asks; there‘s no indication of a deletion failure or error arising.

If there‘s a shades-of-a-log-structured-file-system-that-needs-free-space-to-delete-files issue arising here or in other cases and if Time Machine is not generating a cogent error for failures secondary to an undersized backup target device, please log a bug report or feedback with Apple. Or there’ll be postings 3,001, 3,002, 3,003, etc.

A 2 TB TC drive should have sufficent storage capacity for the typical storage devices and storage churn found in most Macs, or Time Machine should generate better error. If that’s not sorking, there’s a bug, and Apple developer have always requested bug reports for these cases.

The question was.....

What do you do when the Time Capsule runs out of room?

We provided several options as an answer......based on 10 years of experience with Time Machine and different Time Capsule versions. We also said that we don't trust Time Machine to take care of things on its own when the Time Capsule is full.

If your answer to the same question is to do nothing and trust Time Machine to take care of things, then I think we are done here, and the user can decide which path that he wants to take.

I read this as an ordinary question about how to process backuos, in the absence of specific errors. Users often want to know how this stuff works, after all.

In this case? It’s a 2 TB drive. It’s big enough for most typical source devices with typical pruning, barring cases where the backup target device has been shared and filled with unrelated-to-Time-Machine files.