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How To Partition An External Hard Drive For Mac’s Time Machine

Oct 6, 2017 10:00:29 PM / by BaseQi



If you’ve recently gotten an external hard drive that seems a little bit bigger than you might actually have needed it to be, you may be wondering as to the best way that you could put it to use. Sure, it’s good for storing files. You can also try making a full backup of your Mac on it. But if your hard drive is big enough for both, you can try partitioning it so it could serve both purposes at the same time.

This is far easier to do with Macs due to the Time Machine feature that automatically comes with all Mac OS systems. It’s generally recommended for you to format the hard drive yourself rather than buying one that’s pre-formatted: there’s generally no difference, and pre-formatted ones cost much more.

Step 1: Format the hard drive to be compatible with your Mac OS.

  1. Connect the external hard drive to your Mac

  2. Launch Disk Utility, found in /Applications/Utilities/Disk Utility

  3. Select the external hard drive from the drive list on the left, then click the “Erase” tab

  4. Choose “Mac OS Extended (Journaled)” as the format type,then click “Erase” and confirm.

The reason why you need to do this is that while most hard drives have been formatted to be used with Windows OS systems and the Mac OS, there’s an inherent disadvantage to them being left in this format (FAT-32 or NTFS.) In addition, if you wish to use the Time Machine with your external hard drive, you will need to format it exclusively for your Mac.

Step 2: Set the space needed for your partitions.

  1. When the drive has finished formatting, choose the “Partition” tab.

  2. Pull down the “Partition Layout” menu and select “2 Partitions” to split the drive.

  3. Adjust the partition size allocation.

  4. Name the two partitions accordingly.

  5. Choose “Apply”, then confirm the changes by clicking “Partition”.

While it’s generally recommended to split your partitions in half, the ideal size for a Time Machine backup is the size of your entire hard drive multiplied by two (so for example, for a 132GB SSD, you’d want a 264 GB allowance for your backup partition or higher.)


Step 3: Set your Time Machine to backup to your partition.

  1. Go to “System Preferences” from the  Apple menu and then choose “Time Machine”.

  2. Click the “Select Disk” button and wait for your files to show.

  3. Choose the partition named “Time Machine Backup” from the list, then confirm the choice by clicking “Use Backup Disk”.

  4. Let Time Machine backup for the first time.


Your first backup will take a while depending how large your backup is, but succeeding backups should take significantly less time. In addition, you may also choose to encrypt your backup, though the default setting should be fine for those who are new to partitioning.

And that should do it! You’ve successfully partitioned an external hard drive to use for both saving files, and backing up your Mac. There are other options that you can also select while doing this process, but they’re really up to the user’s preference and intentions for the hard drive itself.


If you are looking for ways to increase your MacBook Pro or MacBook Air's storage space, feel free to read the following post: MacBook Air and Pro storage space upgrade, how to get 128GB of space for only $54.




Written by BaseQi

Our company officially started in 2013. Since then, we have fans purchasing our products from all over the world. Our mission is to invent stylish accessories and gadgets for fans around the world.

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