If you’re like me after a year or two you may have outgrown your Time Machine backup and with Hard Drive prices dropping it’s time to get a bigger hard disk to host your Time Machine backup. But starting a new time machine backup on a new hard disk means you lose the continuity with your old backups. Thankfully you can move an existing Time Machine backup from one hard drive to another. Here’s how.
1. Format the new Hard Drive as OSX Extended (Journaled) and make sure ‘ignore file permissions on this volume’ is off.
2. Turn off Time Machine
3. Drag the Backups.backupdb from your old Time Machine Backup to your new Drive. (Yes it’s that simple and it actually works – it’s Apple’s recommended way of doing it!) This may take literally a couple of days.
4. Turn on Time machine and select your new drive.
You can read how to do this step by step in an article by Apple here: Transfer Time Machine Backups.
There’s also a good article about this on c-net. They suggest you use the ‘Copy Exactly’ feature but I did it without this (the way Apple suggested) and it worked fine.
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How to transfer your data from an old macbook to a newer thunderbolt macbook or macbook air. 
How to make a bootable backup of your computer
What about when the destination drive already has a Time Machine backup (e.g. of a different computer)? In my particular situation, I want to use my Mac to copy the backup (all the snapshots) from one external hard drive (Drive A) to another (Drive B), but Drive B already has another computer’s Time Machine backup.
None of the backups belong to the computer I’m using to do the transferring. Finder doesn’t allow me to transfer the folder named named after the computer from Drive A’s Backups.backupdb folder to Drive B’s. I tried moving Drive A’s Backups.backupdb folder into another another root level folder on Drive B (resulting in /Volumes/Drive B/some other folder/Backups.backupdb. But tmutil refuses to work with that Backups.backupdb (presumably because it’s not on the drive’s root level). (Attempting to use tmutil to delete a snapshot in a Backups.backupdb that is not at the first level of the external drive returns “Invalid deletion target (error 22)”. Attempting to use tmutil to compare it with another snapshot returns “Can’t compare a source volume descendant to a snapshot.”)
Wow – complicated. Can you create a disk image on the target drive?
Quick question. Did this and it took forever to copy. when I went back in to TM preferences to awitch tot he new drive I noticed TM was on…even though I was pretty sure I turned it off. The copy seems to work in TM on the new drive even though it doesnt have a few recent backups created durign the 15 hour copy process. is this ok? How can I be sure before I remove the old backups on the original drive.
thanks.
What copy exactly? I looked in Finder preferences and I don’t see that.
What if you had a time machine running on server A where all the macs on your home network backed up to, then you moved the backup drive to server B and started running time machine server there? How do you point your Mac to re-use the existing backups?
If it’s a different machine then the Time Machine backups will be different. It will start again making a new backup.
My Mac completed that it wasn’t the correct format and want me to format it as OS X Extended (Journaled) case-sensitive
I tried this a couple of times following the directions exactly as shown above and on Apple support. I want to transfer TM from 2 Tb Drive to a 4 Tb drive. It never worked. First, it took about 22 hours to what I thought was the full transfer, then the transfer said it was transferring 0 bytes of x Tb to x Tb and it would be 5 seconds. I let it keep running overnight; even though the number of TB’s had increased, it still said 5 seconds to go. When I checked the “get file info” through Finder on new drive, said that I only had one 400 Gb remaining on my 4 Tb drive. Yet, the original 2 Tb drive had over 200 Gb remaining.
My plan was to use my new 4 Tb for both the iMac and a MacBook air.
I went on Apple forums and found the suggestion to try cloning through restore and got error not allowed.
Why would the TM backup file expand from approx 1.75 Tb (on my 2 Tb drive) to over 3.6 Tb on my 4 Tb drive?
This may be a moot point now as I’ve decided to use Acronis for my backups. Still would like to know what went wrong and if others had the same issue
Having same problem as Donn. Only have 1.7T on old TM drive, but on 4t HD showing 2.75 TB of 2.75TB and it just keeps on climbing. Looked on Disk Utility and it shows only 1.73TB used on new HD. Does anyone have any ideas?
I was trying to copy from 500GB HDD which backup took only 250GB to a new 1TB HDD it took 4 days and fill up the 1TB (only 14 days out of 35 days of backup folders) and it says not enough disk space. Anyone can advice?