Hello!

On my mum's iMac, a message now appears every hour: "Time Machine could not create a backup this time on your HD."

Now what? It just doesn't seem to work. My mistake? HD full? Should I just renew the TimeMachine backup, doing a new one for the moment?

Now what?

Greetings,
PeterParker

[andi*pandi]

Either the HD is full (easy to check) or perhaps the HD has got issues. Do a diagnostic on it? Can you manually copy files to it?

Well, if it is full, TimeMachine should delete old files itself, I thought, without my intervention. The external disc - for TimeMachine - is now full, that's true, only 4 GB left, 316 GB filled. That's strange. I can check and "First Aid" says the disc should be repaired, but can't do so.

I can renew the backup, erasing the external drive and create a new backup. But that isn't the idea, right? TimeMachine should handle everything on its own. Weird...

[reader50]

Sounds like the disk became corrupted when TM had it nearly full. Disk First Aid may be objecting because it doesn't have enough room to work.

You could reformat it and start over. But maybe a less drastic step would work. Open your TM volume, go to the backup snapshots.

(time machine volume)/Backups.backupsdb/(your computer name)/the snapshot folders

Trash the oldest one, then empty the Trash. See if this frees up enough space for Disk Utility to fix the volume. Emptying the Trash will take longer than usual.

If Disk Utility still can't fix it, trash the next oldest snapshot or three, empty Trash, and try again. If DU still can't fix it, it's probably something a better utility would be needed for, like Disk Warrior. If you don't have that, then you might as well reformat the backup drive.

[P]

4GB should be enough for Disk Utility to work, though. I wonder if the drive is not damaged. What does Disk Utility say more exactly?

Hello,

I hope the drive is not damaged. TimeMachine says the drive would be "writing protected", lacking for a better English word. Disk Utility says it simply can't repair the drive and to reformat it.

I have a question. Isn't it right that the drive is completely full? I am a bit fearful that the drive is full for the first time, ever sine we created the TimeMachine backup. Already with this first time, it doesn't seem to work, as TimeMachine should erase some backups on its own to free up more space.

Anything wrong with my thinking? Is it a problem of my understanding?

Greetings,
PeterParker

[reader50]

4 GB free on a 320 GB drive means it is almost 99% full. Under normal circumstances TM is fine with this. I suspect directory corruption, and the error message is likely that the volume is being mounted read-only.

The 1% free will be heavily scattered across the volume. Perhaps there is no fragment large enough to rewrite the directory itself.

If you can't delete anything to free up space, and do not have DiskWarrior or TechToolPro, then a reformat is the only easy choice.

If the drive is failing, a reformat will fail too.

I'm with my mum now. I can't delete anything on the external drive, it won't let me. I can use TimeMachine though, to restore files.

[donaldkepler]

I had the same symptoms with a 2012 MacBook pro (came with a Yosemite already installed) using my WD ‘My Passport’ USB drives for Time Machine data backup.
The solution of your problem is to erase and reformat the external drive using the help of Disk Utility as discussed here.
I had a spare drive, so in order to not to lose the data backup, I did the below mentioned tasks:
1. First erase the spare drive
2. Now, use the Disk Utility to ‘restore’ the backup drive’s volume to the erased drive if the Disk Utility window show ‘First Aid; Erase; RAID; restore" as options not "First Aid; Erase; Partition; RAID; restore’
After that, you would not face any problem.