Switching Partition Scheme GUID/MBR on external hard drive

Question

Switching Partition Scheme GUID/MBR on external hard drive

Hello!

I use a MacBook Air with an Intel Processor, Mavericks 10.9.5 and Time Machine.

I am about to format and create partitions on my external hard drives. I will primarily use them to backup data from my Mac with Time Machine.

I need to change the size of the partitions and since I used the MBR partition scheme when formatting them from the beginning, I can not change that without re-formatting.

I can not understand how come I have the MBR format, since this is not the default and when I created my backup hard drives a few years back I was totally new at Mac. (Maybe that's the reason?) But any how, that's what I chose then.

I was not too familiar with the different types of schemes, so I have done some reading today and I have decided to go with the GUID-format.

I'm planning on dividing my hard drives into 3 sections:

1700 GB for backing up my Mac - Mac OS Extended (Journaled)
250 GB 1 for storage of any files from the Mac -Mac OS Extended (Journaled)
50 GB for storage of files to/from Mac/PC - ExFat (Btw, that really is the only downside with switching to Mac, the pain when having to use a PC.)

If you know a bit more about the different schema types and have any comments or recommendations, please feel free to drop me a line.

/Cecilia

PS I'm a bit concerned that there is a really good reason why I had MBR and now I just don't know what it is.

MacBook Air, OS X Mavericks (10.9.5)

Posted on Aug 7, 2015 2:25 PM

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Answer 1

Kappy

Level 10

362,023 points

Aug 7, 2015 2:36 PM in response to CCKayWithAKay

The MBR and format are often set at the factory. You would have needed to make the change before using the drives. In order to change the partition map from MBR to GUID you will need to re-partition the drives which is a destructive process - all data are erased. You will get the most performance from the drive by using GUID.

Drive Partition and Format

1. Open Disk Utility in the Utilities folder.

2. After Disk Utility loads select the external hard drive (this is the out-dented entry with the mfgr.'s ID and size) from the left side list. Click on the Partition tab in the Disk Utility main window.

3. Under the Volume Scheme heading set the number of partitions from the drop down menu to three. Click on the Options button, set the partition scheme to GUID then click on the OK button. Size each partition as you want. Set the format for the first two partitions to be Mac OS Extended, Journaled and set the last partition to use ExFAT. Click on the Apply button and wait until the process has completed.

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Answer 2

Aug 7, 2015 2:55 PM in response to Kappy

Hello Kappy!

Thanks for you comment.

When I first started using my hard drives I re-formatted them and created several different partitions. At least one for each file format there is.

(Since I did this and did not use them as set from the factory, I must have chosen MBR willingly. Can't for the life of me understand why.)

I was a bit unsecure what I needed and how it would work so I thought it was a good idea to have all kinds of formats. It turns out I only need two formats.

So, now that I know a bit more of what I want and need, I'm ready. I know the data will be destroyed when formatting, but thanks for pointing that out. It has been taken care of.

My biggest concern and question was on a more theoretical level: is it a good or bad idea to use GUID. And you have clarified that, when you tell me I will get the most performance from my drive using GUID. Exellent, I'm on the right track here.

The only downside here is that it takes FOREVER to produce the first backup.

Thanks again!

/Cecilia

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Answer 3

Kappy

Level 10

362,023 points

Aug 7, 2015 3:05 PM in response to CCKayWithAKay

Each first backup is a full one and it will always be the slowest. 🙂

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