Mac – Move an old Time Machine folder (NOT volume!) to a different disk

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I have an old Time Machine backup that I moved from its volume to a folder on a different disk. Now I want to move it to yet another volume. The problem is that the volume where the backup folder is now shows about 90 GB of used space, while the folder itself shows a size of about 240 GB and I don't have that space available at the moment.

My question is: how can I move this folder?

Best Answer

You're probably seeing the result of hard links in the file system, which can result in counting the same file(s) more than once.

This is common in UNIX-like backup solutions, including Time Machine. The actual data usage is only 90GB, so a hard-link-friendly tool like rsync should handle the move correctly.

Per Wikipedia's article on hard links:

The term is used in file systems which allow multiple hard links to be created for the same file.

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Mac – Time Machine forgets old backups

The system will delete old backups if it has an estimate that it will need the space for the impending backup. Normally the system over estimates a backup by 2 to 4 GB in routine use, but I have seen some cases where it had estimates of 250 GB or more due to some folder changes. Even without an error in estimation, you could have attached an external drive that increased this estimate drastically.

Only you have the logs and data to know how plausible this is. Check out BackupLoupe if you like to have better measurements on how each backup differs in size from the others.

For this reason, I periodically duplicate my Time Machine drives (or choose to rotate them monthly) so that if there is a bug, I can look when I swap in the new drive to make sure I don't lose some of my older history.

MacOS – How to manually delete old backups to free space for Time Machine

Be careful with sudo and making sure you pick the correct Mac's files since there is no undo or confirmation of the following command:

sudo tmutil delete /Volumes/drive_name/Backups.backupdb/old_mac_name

The sudo command needs your password (and it won't echo to the screen, so just type it and pause to be sure you're dating the correct files before pressing enter). If you want to be safer, you can pick one snapshot to delete first to be sure the command works as intended. This is nice since it could take hours to clean up some larger backup sets and you want to leave the Mac confident it's deleting the correct information store.

You can use the tmutil tool to delete backups one by one.

sudo tmutil delete /Volumes/drive_name/Backups.backupdb/mac_name/YYYY-MM-DD-hhmmss

Since tmutil was introduced with Lion, this will not work on earlier OS versions.

If you want to get the current directory of backups (there can be multiple destinations defined and only one will be "current")

sudo tmutil machinedirectory

Best Answer

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