How to Partition an External or Internal Hard Drive in OS X.
Partitioning a hard drive can be a tedious and challenging task. However, once you understand how this process works, it becomes much less scary. So why would you need to partition your disk?
When I was in college, like many other students, I owned a MacBook Pro because of its ease of use and its minimalist aesthetic. I didn’t think that some of the applications I needed for school were not Mac compatible. Then I thought about partitioning my drive to run Windows on Mac.
In addition, I had an external hard drive that I wanted to use with both OS X and Windows. In this article, I am going to show you how to split internal and external hard drives on Mac.
Before you start, you should back up your entire Mac using Time Machine. Even if you don’t mess up anything, chances are good that the OS will mess up your system.
External drive section
If you have a large external hard drive, you can easily partition it to use the entire drive. I’ve used a 1.5TB external drive with my Mac, but never used more than 1/4 of its capacity.
Instead, this is how I partitioned my disk, which made it much more useful:
- 33%: Mac (Extra Storage) – 500GB
- 33%: Mac (Time Machine backup) – 500GB
- 33%: Windows (additional storage and backup can be in the same partition) – 500 GB
As you can see, each section can have its own file format. If you have an even larger disk, you can create even more partitions for other operating systems like Linux, etc.
To partition your disk, go to the Spotlight section at the top of your MacBook screen (notification bar) and type Disk Utility.
On the left go to the EXTERNAL tab.
Yours will look a little different than mine. Under the heading External on the left side, you should have one hard drive instead of three (I’ve already partitioned mine). Go to this external hard drive and partition it according to your needs.
NOTE. If your external hard drive is not formatted for the Mac operating system, you may need to initialize it first and then wipe it. It’s very simple:
- From the outer tab on the left, select the drive you want to use.
- Then select the Erase option at the top
- Once there, give it a name and format it to Mac OS Extended (logged).
- For schema, you can choose GUID, MBR or Apple. If you only use the disk for storage, it doesn’t matter which one you choose. However, if you plan to boot from disk, you should select MBR for Windows and Linux and GUID for OS X. If you plan to use disk for Boot Camp, you should also select GUID.
Note that you can also click on Security Options and choose from different security levels. By default, OS X will use the fastest method, which does not erase data from disk. If you move the slider to the “Most Secure” position, it will conform to the DOD standard for erasing data by overwriting data 7 times. This will prevent anyone or any software from recovering previously written data from the disk.
OS X may ask you if you want to use the drive for Time Machine backups, but you should select Decide Later if you don’t want to use the entire drive for backups. You are now ready to partition your external drive!
Navigate to the top where there are options: First Aid, Partition, Erase, Recover, Mount, etc. Select Partition and create partitions according to your specific needs. In my case, I chose a size of 500 GB, which is a third of the disk.
Select how you want to partition the disk (go back to my percentages as this is what I used in the screenshots here), select Apply and then click Split. After that, the separation will take a few minutes, so be patient!
Once completed, a green checkmark should appear next to your disk and it should be written that the operation was successful. Now select “Done” and you’re done with the first section.
Now, to split the rest of the space, click Untitled under the Outside section, and then click Divide again.
Give the section a name, size and format. Since this will be Windows storage, I chose MS-DOS (FAT). You can also opt for exFAT if you like as it is compatible with both Windows and Mac.
Internal splitter engine
Partitioning an internal hard drive is almost the same as the procedure you should follow, but slightly different in how it is implemented.
Since you already have OS X installed on your internal disk, when you click Split and choose a size, you will notice that you cannot create a partition that is smaller than the amount of space already used on the disk.
My internal drive was already using 359 GB of space, so when I typed in 200 GB, it automatically changed it to 359 GB and brought up a message that the first volume could not be deleted and the volume could not be split because the resulting volumes would be too small.
So if you want to create an additional partition, the first thing to do is create a partition that will include OS X and give you extra space to install programs, etc. Below I left the name Macintosh HD and made a 500GB partition. This means that the partition on which OS X is installed has about 140 GB of free space for additional data.
Basically, we are just shrinking the original partition, which occupied the entire disk, to a smaller size. Then we will split the free space however we like.
As you can see, I made the original 500GB partition instead of 1TB, which frees up 500GB of disk space to create other partitions. As with the external hard drive, after creating the partition, click Untitled, but this time under the Internal heading and click Partition.
This is pretty much all there is to disk partitioning in OS X. Hope it worked for you. Enjoy!