The Time Machine Monster that Devoured Cleveland....Help!

Question

My Time Machine backup file grew to monster size. How big is this monster? Read on.
It all began one quiet afternoon. Hard drive failure on my iMac. No worries. I have a Time Machine backup on an external disk.
But that external disk seems a bit twitchy. So before I do anything else, I copy it's "backups.backupdb" file to the desktop of my Macbook. Now I have two copies, just in case.
Hard drive replacement goes fine. Restore via Time Machine from the external disk does too. I'm up and running.
I erase the external drive and do a fresh Time Machine backup onto it. Everything is still good. If I want the earlier backups, the ones made before my drive failure, I have a copy on my MacBook, right? This is where the mystery takes foot.
I try to save the "backups.backupdb" folder from my MacBook to a new external drive. I connect a 1TB drive and drag the "backups.backupdb" folder to it. Several hours later the "preparing to copy" window has counted millions of files to copy. I think it was about fifteen million. The system says that there is enough space in the 1TB drive to copy that folder.
What? The original "backups.backupdb" folder was created within a 250 GB partition!!!!
I go to the "backups.backupdb" folder on my laptop and "command i" it to calculate size. This takes hours and when it's though, my system says that the "backups.backupdb" folder is 12.9 Terabytes !!!!!! I wish I had thirteen T of storage on my laptop!
The "backups.backupdb" is clogging my laptop. Is there any way to copy and save it? Or do I just have to erase it to get rid of it?
Thanks in advance. And I will thank you afterward too if you can give me any clues.

Answer 1

To delete huge amounts of data the Terminal is your friend. It will still take a long time, but won't go through so many steps as using the Trash and it won't block your Trash while it runs in the background.
01. Launch 'Terminal', in the '/Applications/Utilities/' folder.
02. Enter ...
sudo bash
..., and then press the '<return>' key.
03. Enter an administrators' password, and then press the '<return>' key.
04. Enter ...
rm -rf
... (make sure to press the 'space bar' after the 'f' in 'rm -rf', as in 'rm -rf ').
05. Drag the backups.backupdb folder onto the 'Terminal' window.
06. Click once on the 'Terminal' window.
07. Press the '<return>' key.
08. Wait
Next time you want to manually copy a Time Machine backup, open the backups.backupdb folder, then the folder named after your computer and copy just the folder named after the date and time of the latest backup (if you look inside you will see folders named after all backed up volumes).
Time Machine uses hard links to achieve incremental backups. Let me explain. Any file on your computer has a physical location on the hard drive and a hard link which points at this location. It's as if you are only visible if your friend stands next to you and points at you and as soon as he stops pointing at you, the world cannot interact with you anymore. You are still there, physically, but as far as anyone else is concerned, you are gone. This is how files are deleted: by removing the hard link. The file is still there and until the system decides to write some other file onto that location on the hard drive special recovery software can detect those files without hard links and offer to recreate them, making the files accessible again.
A file can have more than one hard link pointing at its physical location. It looks to the system that there are multiple copies of the same file, each taking up x amount of space. But in reality there is only one physical copy on the hard drive. You can delete any of the hard links (which just look like an ordinary file) and the file remains intact, until you delete the last one.
Hark links take up virtually no space. So each time Time Machine makes a backup it simply creates a hard link to files that have not changed since the last backup. If you are backing up external drives as well and you are running Time Machine while those drive are not connected it will even create hard links to files on those drives from the last available backup.
Hopefully all this makes some sense.
In the end, there is nothing special about the way Time Machine backups are stored on disk. The Finder just sees it as separate copies of the same files, one copy for each backup. That is why, when you "command i" it take so long and you get 12.9 terabytes: it adds up every hard link (as I said the hard link itself takes up no space, but it points at a physical location and reports back the physical size of the file it points at) as a separate file.