Repartitioning a fusion drive

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Repartitioning a fusion drive

I needed to use bootcamp to install Windows 10 on my iMac for school. The first time I tried to use bootcamp it failed half way through the process of creating a partition, so I went back and deleted it (at least I thought) using bootcamp. The second time it worked flawlessly and I now have a 506 GB BOOTCAMP HD with Windows 10 installed and running to perfect. However, as I went back to check to make sure everything was perfect, I noted that I had a computer of my Macintosh HD drive, which I didn't have before. So I now have 3 partions; a 1.61 TB Macintosh HD, a 801.44 GB Macintosh HD and a 506 GB BOOTCAMP. Does anyone know how I would repartition the two Macintosh HDs back into one single partition? I have a 3 TB hard drive, but in the storage menu it is missing the 801.44 GB from the second macintosh GB. Any ideas on what to do? Thanks.

Here is what it looks like:

iMac, OS X Yosemite (10.10.5)

Posted on Oct 6, 2015 8:06 PM

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Answer 1

Loner T

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Oct 6, 2015 8:30 PM in response to wvburg

Do you have a Fusion drive? Please post the output of the following Terminal commands

diskutil list

diskutil cs list

sudo gpt -vv -r show /dev/disk0

sudo fdisk /dev/disk0

If you have a Fusion drive, then

sudo gpt -vv -r show /dev/disk1

sudo fdisk /dev/disk1

The "sudo" commands will prompt for your password, and it will not be echoed back. You may also see a warning about improper use of "sudo" and potential data loss due to "abuse" of the command.

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Answer 2

wvburg Author

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Oct 7, 2015 9:59 AM in response to Loner T

Yes, I have a 3.12 TB Fusion Drive. Should I still put that second sudo commands in Terminal even with potential data loss?

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Answer 3

Loner T

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Oct 7, 2015 10:13 AM in response to wvburg

If you use a rm command then you can lose data, but the given commands just read the information from the disk.

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Answer 4

wvburg Author

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Oct 7, 2015 12:58 PM in response to Loner T

Here is the result of the second command you sent me:

gpt show: /dev/disk1: mediasize=3000592982016; sectorsize=512; blocks=5860533168

gpt show: /dev/disk1: Suspicious MBR at sector 0

gpt show: /dev/disk1: Pri GPT at sector 1

gpt show: /dev/disk1: Sec GPT at sector 5860533167

start size index contents

0 1 MBR

1 1 Pri GPT header

2 32 Pri GPT table

34 6

40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B

409640 3305004560 2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC

3305414200 1269760 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

3306683960 456

3306684416 988278784 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

4294963200 2040

4294965240 1565305744 5 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC

5860270984 262144 6 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

5860533128 7

5860533135 32 Sec GPT table

5860533167 1 Sec GPT header

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Answer 5

Loner T

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Oct 7, 2015 3:34 PM in response to wvburg

Due to limitation of legacy Windows (BIOS/MBR) and 2TB limit, the start address of the Windows volume must be within the first 2TB sector addresses of the disk. If your Windows installation is smaller than 1TB, remainder of the disk is merged into OSX using a CoreStorage volume. This is why you see your Macintosh HD entry twice, because it is in two parts, with BC/Windows in the middle. This is normal on a 3TB Fusion drive with a legacy Windows installation.

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Answer 6

wvburg Author

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Oct 7, 2015 5:55 PM in response to Loner T

So does this mean the 801.44 GB of the second Macintosh HD is not going to be used? Also, would the only way to repartition my hard drive be to restore my whole computer back to factor settings? Thanks for the help!

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Answer 7

Loner T

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59,471 points

Oct 7, 2015 6:14 PM in response to wvburg

wvburg wrote:

So does this mean the 801.44 GB of the second Macintosh HD is not going to be used?

It will be used. In a CS volume, the SSD part contains the frequently used files, while less often used files can end up on the HDD part.

Also, would the only way to repartition my hard drive be to restore my whole computer back to factor settings? Thanks for the help!

If you remove BC/Windows it will merge the chunks of disk space back into a whole volume. It may still have separate underlying physical parts.

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