I did a reinstall of my system 10.6.8 using combo and now Time Machine thinks that the drive contains much more data that it actually does. When I try a TM backup I get this dialogue box.


"Time Machine could not complete the backup.

This backup is too large for the backup disk. The backup disk requires 201.59GB but only 159.43GB are available.

Time Machine needs work space on the backup disk, in addition to the space required to store backups. Open Time Machine to select a larger backup disk or make the backup smaller by excluding files."

In fact the HD only contains 86.38 GB.

I did as the dialogue box instructed and excluded a few very large folders. At that point the Time Machine started to do a backup. However, the status bar said it was doing a much larger backup...about 126GB.

How do I get Time Machine to understand that the drive only contains 86.38 GB?

What's the capacity of the disk you're trying to back up to? How much of that is taken up by the existing Backups.backupdb folder?

Where do I locate the Backups.backupdb folder? Is it an invisible file? I tried Spotlight but it didn't find it.

If there's nothing on the backup volume aside from your Time Machine backup, you can just do a Get Info on it (with the backup disk selected, type ⌘-i) to get Capacity, Available, and Used stats.

It may be the case that your reinstallation of OS X has Time Machine thinking it's backing up an entirely new volume. The error message you received seems, via perusal of Google search results, typically experienced by those who have restored the entire contents of the internal drive, or replaced the drive itself and restored the old drive's contents to it, but there seems to be enough mystery surrounding when and why that happens to suggest that Time Machine can be subject to confusion when significant changes to the disk being backed up occur between backups.

"The backup disk is full" may provide some insight. (In particular, scroll down to "This backup is too large . . . (all OSX versions; sample from Mountain Lion)".)

The Backups.backupdb folder is located in the sparse disk image with the name of your computer that you will find in the Data folder on your Time Machine drive. You have to mount the sparse disk image before you can find or see the file. At least that is where it is found on my Time Capsule.

NOTE: it can take a l - o - n - g time to calculate the size of either the sparse image file or the Backups.backupdb file.

My Time Machine backup is on one partition of a multi-volume drive, and there's no sparse image involved; clicking on the volume in a Finder window simply reveals the Backups.backupdb folder (clicking on that in turn reveals two folders—one for the old mini which is not currently in service, and one for the new one, but that's a different story).

It does take a l - o - n - g time to calculate the size of the Backups.backupdb folder, which is why I suggested simply getting info on the backup volume itself in my followup post. If ryck has other data on the volume, though, a Get Info on the volume will muddy the waters as far as the problem at hand is concerned.

I should point out that my Time Machine volume was so anointed back when I was running OS X 10.5; when I upgraded my system, I simply continued using it as such. I guess it's possible that were I to start from scratch under OS X 10.8, I'd see the same configuration as joemikeb...

This page suggests that the Data folder and sparse image described by joemikeb are specific to Time Capsule applications.

The Drive is a partition on a 320GB OWC drive that is partitioned 50/50 with my Super Duper clone on one half and Time Machine on the other.

The Backups.backupdb folder has a document that says:

Name: 2013-03-24-16509.inProgress
Kind: package
Size: 37 KB

By way of history, I had previously used the full 320GB for the SD Clone, with my Time Machine on a separate 80GB LaCie drive (with several files excluded). However, I only ever use Time Machine to pull up previous versions of written documents I am editing and have never thought about it as the backup in case of main drive failure. SD Clone is for that.

Therefore it seemed goofy to me to keep two drives on my desk when one would suffice. Hence the 50/50 partition. This worked absolutely fine and both backups were done from scratch without issue.

What has transpired in the meantime is that I resolved a different problem by running 10.6.8 update combo.

When Time Machine next tried to do a backup I got the first of the dialogue boxes telling me that there was not enough room with things like "The backup disk requires 201.59GB but only 159.43GB are available"

Assuming the main drive must be keeping the original version of the pre-10.6.8 drive content on the Time Machine, I erased it. That made no difference.

I have now tried hooking up the original LaCie backup drive and it generates the same no-can-do with similar giant numbers. I have also erased it, but to no avail. FYI, its Backups.backupdb folder says:

Name: 2013-03-25-081234.inProgress
Kind: package
Size: 25 KB

Well, now I'm confused.

Are you saying you've erased two Time Machine volumes in an attempt to address this issue? I understand that you don't regard Time Machine as your main backup, but that still seems like radical surgery even if you "only ever use Time Machine to pull up previous versions of written documents," since you can now no longer do so. Or am I misunderstanding you?

It seems more than likely that the problem resides on your Mac's drive, if the same symptoms manifest themselves when you're connecting to two different blank external volumes. I think I would have suggested resetting Time Machine on your Mac before erasing anything on any backup drives. See Full Reset of Time Machine for details.

Yes...but the surgery isn't quite as radical as it appears.

I only just partitioned the drive a couple of weeks ago, and there wasn't much backup data to worry about. So, it wasn't like I amputated a limb, leaving a stump, but more like amputating something that wasn't much more than a stump.

Also, going back to documents is never more than a couple of weeks (once I've finished the editing, the items are usually published within the next two weeks).


I did that this morning but it didn't generate any positive results. Here's the sequence after finishing the complete reset:

1. TM acknowledged that 159.43GB of 159.73GB were available.

2. TM than began calculating changes which included the exclusion (TM's decision) of more than 547,000 items.

3. TM began the backup and almost immediately said it could not complete it because it required 183.05GB but only 159.43GB were available. (Note: the drive being copied only has 85.54GB used.)


That's what I suspect (not based on any great knowledge of how these things work) and I also suspect it's related to the fact that I had the 10.6.8 Combo update done in the midst of all this.