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Level 1

104 points

Can't create Windows partition on roll-your-own Fusion drive

I've created my own Fusion drive from an internal SATA HDD and an SSD in the optical drive PATA port on a 2008 iMac. I now want to use Boot Camp. Boot Camp won't create a partition on my Fusion drive because, apparently, it thinks I'm using an external drive. When I use Disk Utility to partition the drive, it creates a 300GB partition when I've asked for a 47GB partition, leaving me almost no free space on my main partition.

What's going on here? Why is Disk Utility misbehaving? Is there a way to make Disk Utility create a ~40GB partition on my Fusion drive? Perhaps by creating it as an HFS+ partition, then reformatting it, or using the command line version of Disk Utility? I'm reticent to experiment as this is my main machine, and I've heard horror stories about hosing drives in this manner.

iMac, OS X Yosemite (10.10)

Posted on Feb 16, 2015 9:31 AM

45 replies

Zarquon42 Author

Level 1

104 points

Feb 16, 2015 6:15 PM in response to Loner T

I tried

diskutil cs resizeStack 1E68BA1C-6FC8-4650-BFC8-F2F6D05C8B98 4A8460C6-E2FD-4226-B136-BB1FA8185D1C 587g fat32 BOOTCAMP 0g

and the result was essentially identical to what happened when I used Disk Utility: The Windows partition took up roughly half of the total space, leaving about 20gb of free space on Jane's Brain. I then (possibly foolishly) tried to fix it with Disk Utility, clicking the "-" button; that merged it with the eDrive below it (though DU said it would merge it with the partition above it). I then tried to remove that partition with DU, but it reported extents errors, as did diskutil when I tried

diskutil cs resizeStack 1E68BA1C-6FC8-4650-BFC8-F2F6D05C8B98 0g

So I rebooted into my Recovery partition, ran Repair Disk with Disk Utility, then ran the above command again successfully (while started from the boot drive; it wouldn't work from the Recovery partition).

Loner T

Level 9

59,477 points

Feb 16, 2015 6:24 PM in response to Zarquon42

Do you have a backup of eDrive? If yes, erase it, erase the bootcamp partition, and make sure they are formatted as Free Space, so that it can be coalesced into a single Free Space extent. You should then be able to extend "Jane's Brain" and absorb the Free space. Once you have it in the final state, then a new resizeStack can be tried.

Zarquon42 Author

Level 1

104 points

Feb 16, 2015 6:30 PM in response to Loner T

I did that already, after the first attempt. Sorry, I forgot to mention that before I did diskutil cs resizeStack 1E68BA1C-6FC8-4650-BFC8-F2F6D05C8B98 0g, I erased the remaining large partition (which was then eDrive) with Disk Utility. So what you're asking for is exactly what I did after my first attempt failed.

The eDrive can be created in a few minutes by TechTool. It's not essential, but it's nice to have.

Loner T

Level 9

59,477 points

Feb 16, 2015 6:29 PM in response to Zarquon42

When you erase the partition via DU, in the drop down, make it free space. Do the same with Bootcamp. This will give you contiguous address space from GPT3 till the end of the disk.

Zarquon42 Author

Level 1

104 points

Feb 16, 2015 6:35 PM in response to Loner T

Actually, deleting the BOOTCAMP partition put my disk back into its original state:

gpt show: /dev/disk1: mediasize=640135028736; sectorsize=512; blocks=1250263728

gpt show: /dev/disk1: PMBR at sector 0

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

gpt show: /dev/disk1: Sec GPT at sector 1250263727

start size index contents

0 1 PMBR

1 1 Pri GPT header

2 32 Pri GPT table

34 6

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

409640 1224892768 2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC

1225302408 1269760 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

1226572168 23429256 4 GPT part - 48465300-0000-11AA-AA11-00306543ECAC

1250001424 262271

1250263695 32 Sec GPT table

1250263727 1 Sec GPT header

So should I remove the eDrive and try again, or is there a way to do this while leaving the eDrive intact? Techtool won't create an eDrive on a Fusion disk with a Bootcamp partition (though in principle I could make one by hand if needed if I can partition things correctly).

Thanks again for your continued help with this.

Zarquon42 Author

Level 1

104 points

Feb 16, 2015 6:38 PM in response to Zarquon42

Ach, I forgot to mention previously that I had recreated the eDrive before trying diskutil cs resizeStack 1E68BA1C-6FC8-4650-BFC8-F2F6D05C8B98 4A8460C6-E2FD-4226-B136-BB1FA8185D1C 587g fat32 BOOTCAMP 40g.

It probably is in fact the case that you can't have more than two partitions on a Fusion Drive, as Apple repeatedly states. I'm going to remove the eDrive and try again. I can always put one on a USB stick.

Loner T

Level 9

59,477 points

Feb 16, 2015 6:40 PM in response to Zarquon42

I suggest you put the eDrive on the 256Gb disk.

Zarquon42 Author

Level 1

104 points

Feb 16, 2015 7:06 PM in response to Loner T

Nope. Same result.

gpt show: /dev/disk1: mediasize=640135028736; sectorsize=512; blocks=1250263728

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 1250263727

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 648296544 2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC

648706184 1269760 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

649975944 1912

649977856 78123008 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

728100864 522162831

1250263695 32 Sec GPT table

1250263727 1 Sec GPT header

Loner T

Level 9

59,477 points

Feb 16, 2015 8:20 PM in response to Zarquon42

Erase Bootcamp partition, and run it without the pvUUID

diskutil cs resizeStack 1E68BA1C-6FC8-4650-BFC8-F2F6D05C8B98 587g fat32 BOOTCAMP 40g

The resizeStack first splits the 627g into two parts, roughly 324g each, makes GPT2 that size, and then since you are asking for 40G, leaves the remainder as free space. You can try

diskutil cs resizeStack 1E68BA1C-6FC8-4650-BFC8-F2F6D05C8B98 324g fat32 BOOTCAMP 40g jhfs+ OSX-Remainder 262g

then use diskutil cs to add the OSX-Remainder back into the CS volume using diskutil cs addDisk.

Zarquon42 Author

Level 1

104 points

Feb 20, 2015 10:18 AM in response to Loner T

diskutil cs resizeStack 1E68BA1C-6FC8-4650-BFC8-F2F6D05C8B98 324g fat32 BOOTCAMP 40g jhfs+ OSX-Remainder 262g

results in

Error: -69787: The partition cannot be resized; try reducing the amount of change in the size of the partition

Sigh. Why is this so difficult? What's odd is that diskutil seems convinced that the partition size of Jane's Brain after diskutil cs resizeStack 1E68BA1C-6FC8-4650-BFC8-F2F6D05C8B98 587g fat32 BOOTCAMP 0g is in fact 587GB, when Disk Utility shows it as 317GB.

Loner T

Level 9

59,477 points

Feb 20, 2015 10:41 AM in response to Zarquon42

1. Try reducing the 262g to say 250g and test.

2. There is confusion on LVG and LV size. If you post the GPT it is probably an easy explanation.

Zarquon42 Author

Level 1

104 points

Feb 20, 2015 11:35 AM in response to Zarquon42

Er…I've been using the wrong numbers. My Fusion drive is 882gb, not 687gb. Once I corrected the numbers,

diskutil cs resizeStack 1E68BA1C-6FC8-4650-BFC8-F2F6D05C8B98 4A8460C6-E2FD-4226-B136-BB1FA8185D1C 842g fat32 BOOTCAMP 0g

worked great.

*facepalm*

Thanks for your help.

Loner T

Level 9

59,477 points

Feb 20, 2015 11:41 AM in response to Zarquon42

Can you post the GPT and MBR for the record?

Zarquon42 Author

Level 1

104 points

Feb 20, 2015 11:43 AM in response to Loner T

sudo gpt -vv -r show /dev/disk0

gpt show: /dev/disk0: mediasize=256060514304; sectorsize=512; blocks=500118192

gpt show: /dev/disk0: PMBR at sector 0

gpt show: /dev/disk0: Pri GPT at sector 1

gpt show: /dev/disk0: Sec GPT at sector 500118191

start size index contents

0 1 PMBR

1 1 Pri GPT header

2 32 Pri GPT table

34 6

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

409640 499446368 2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC

499856008 262144 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

500118152 7

500118159 32 Sec GPT table

500118191 1 Sec GPT header

sudo gpt -vv -r show /dev/disk1

gpt show: /dev/disk1: mediasize=640135028736; sectorsize=512; blocks=1250263728

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 1250263727

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 1169780832 2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC

1170190472 1269760 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

1171460232 1912

1171462144 78800896 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

1250263040 655

1250263695 32 Sec GPT table

1250263727 1 Sec GPT header

Loner T

Level 9

59,477 points

Feb 20, 2015 11:53 AM in response to Zarquon42

The MBR (Fdisk) also, please. 😉

Can't create Windows partition on roll-your-own Fusion drive