Upgrading an AirPort Extreme’s USB Hard Drive Used for Time Machine

There are two Macs in our home using Time Machine to back up to a 1TB USB hard drive connected an AirPort Extreme 802.11ac. After the painful process of changing the country of my iTunes Store account when I moved to the US, I was forced to keep a local copy of all the movies and TV shows I had purchased. This is backed up as well, so the 1TB drive began to run out of space.

The drive would soon need to be replaced with something bigger, so I purchased a 2TB Seagate Expansion portable hard drive. However, I didn’t want to just swap the drive connected to the AirPort Extreme and start backing up the Macs from scratch–I wanted to retain the existing backup history1. The AirPort Extreme’s Time Machine support has had a spotty history so I was a little wary about whether it was even possible to even do.

After a search online didn’t yield any meaningful results, I decided to wing it and see if I could just plug both drives into my Mac. Turns out, this works perfectly. Here’s what I did:

  1. Make sure both the USB disk attached to the AirPort Extreme was not mounted on either Mac
  2. Disconnect the USB drive from the AirPort Extreme
  3. Connected the new USB drive to the Mac and created a single HFS+ volume named Time Machine (this is the same name as the existing USB drive)
  4. Connected the old USB drive to the Mac, then copied the disk images to the new drive

Both drives, along with my MacBook Pro, are equipped with USB 3.0, so I left the Mac for a few hours to copy 800GB between the drives while I ran some errands. Once this was finished, I then connected the new USB drive to the AirPort Extreme and restarted the base station2.

After the AirPort Extreme powered back up, I started a Time Machine backup on my Mac. The backup worked flawlessly, creating an incremental backup and not, as Time Machine does when it thinks something is amiss, start an entirely new one. I could also view, and restore from, any part of the Time Machine backup history.

  1. I also had plans to use the outgoing 1TB drive for something else. 

  2. I don’t think restarting the base station was necessary but it was worth doing, just to be on the safe side.