I get:

This backup is too large for the backup disk. The backup requires 35.72 GB but only 24.79 GB are available.


Estimated size of full backup: 149 GB

Size of Backups.backupdb on the Time Machine drive is 166 GB and there is 18GB of free space on the drive.

So why doesn't the backup go through? It should be able to delete old files... especially since the current backup size on the drive is less than it is required for the new one.

3 Answers 3


I know what is the problem... I only have one backup on time machine and it won't delete it because it's the only one. So I can either clean up some space on the drive (I have other things there) or just delete the backup and let it run again.

How to delete a backup - from here:

The easiest way is to:

  1. Enter time machine (on the Mac whose backup you want to delete)
  2. Go to the point in time you want to delete
  3. Select the icon that looks like a cog in the finder and choose 'Delete Backup' This ensures the backup catalog remains accurate and the integrity of your data stays intact.

I never had this problem until I tried using my 1TB disk to backup my main drive (256gb) plus my extra drive (750gb). So, just 1 to 1. The problem is, for most cases, TM disk should be at least twice as big (as your data).

You probably have a disk that's too small! And you'll be better off either reducing how much data you want to backup, by excluding some folders from it (under TM options), or simply buying a bigger disk. 2 TB disks are quite affordable nowadays, specially if you consider how much it would cost you to lose your data...

Of course, you can also keep manually deleting backed up data to make the message go away every time it appears... But that will beat most of the advantages of automated backup. In fact, if a backup is not automated, you won't do it as often as you should thus making it most likely a useless backup for when you need it, it shall be outdated.

Now... If that's not your case, then there's this one site resource for all things Time Machine. And this is their relevant article about full disks: http://pondini.org/TM/C4.html (or try the wayback machine).


When TM needs rom it does not delete the entire backup, it looks for files you deleted and no longer needs, and removes those from the backup to make room.

You really should be using a drive that is at least twice the size of your current drive, but that's besides the point.

Are you using Parallels, VMware or Virtualbox? Those tend to have large virtual machine disk images, and need to backup the entire image every time you do a backup. I've seen reference to ways to change the disk image into "slices" to work around that.

If you have anything you can exclude form the backups, like podcasts or your download folder, do that, and then clear out all the "extra" files you have stored on the drive, and see where you end up.

  • No, I don't have VMware or Parallels... I'm already excluding some things from the backup. On the TM backup drive I have some other stuff on purpose - to prevent TM from filling up the drive (with old backups), one latest backup is enough for me... Theoretically it could do a backup with so much space as I have now, but it seems it needs more. I guess I'll delete the existing backup, make a new one and then think more about the issue if it's the same next time. I only want to do incremental backups from there on. If all else fails, I'll free 30GB or so.
    – davidhq
    Commented Jul 13, 2013 at 15:23

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .