Unable to format iMac Fusion Drive.

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Level 1

21 points

Unable to format iMac Fusion Drive.

I'm selling my iMac, 27" late 2012 with 3TB Fusion Drive.

Last night I put it on to do a triple erase to make sure my data isn't recoverable. This morning it looked fine, however I don't appear to be able to do anything with the hard drive. It's now listed on the left in Disk Utilities as "Macintosh HD" but with no parent drive. There's no formatting options, and the partition tab looks fine although everything is greyed out. I also can't unmount the drive since that's greyed out, and when I try to reinstall OSX the drive isn't selectable. I've booted from a USB drive to see if that would help but getting the same options or lack thereof.

I tried contacting Apple support but they weren't very helpful and just suggested I take the machine to my "local" Apple store, which is around an hour away on the bus so not really possible, and I'd like to try to get this fixed. I have a Windows machine I can things from (it's how I made the bootable USB drive), but I have no other Mac here (to plug into the iMac for example), so does anyone have any other options I can try?

I can boot the machine normally, it comes up with the login screen, but it doesn't allow me to log in, so the HD is working and mounted, but not formatted correctly and I can't seem to figure out how to do this.

iMac (27-inch, Late 2012), OS X Mavericks (10.9)

Posted on Dec 9, 2013 5:19 AM

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Answer 1

Dec 9, 2013 10:22 AM in response to ihaveaposse

I don't understand, you erased the drive but you can still boot from it, is this the recovery partition you are booting from or the Macintosh HD partition.

If it is the Macintosh HD partition what did you erase?

Edit.

Your Mac may have the recovery option in Firmware not on your Disk drive but question is still, What did you erase?

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Answer 2

ihaveaposse Author

Level 1

21 points

Dec 9, 2013 10:31 AM in response to rack0 tack0

I did an erase of the main disk (ie the internal one, not the recovery partition), but apparently it didn't actually erase the whole HD. I could "boot" but only to the login screen. All the options to fix the disk or erase it were then greyed out in disk utility.

I've actually (I think, fingers crossed) managed to fix this now by the following method:

1. Downloaded a "pirate" copy of Mavericks DMG from the Internet (I say "pirate" since it's free now but not supplied as a DMG by Apple).

2. Used this on a Windows machine to create a bootable Mavericks USB drive.

3. Booted from this, installed Mavericks on the same HD.

4. Loaded disk utility from the USB, and clicked fix about 10 times until it finally came up asking if I wanted to fix the SuperDrive. It then erased it and joined the drives back together or whatever it did.

I'm now able to boot from the main drive, and currently going through an erase of free space. Although any time I tried to do the higher security 3 pass or 7 pass, it gave me errors saying it couldn't complete what it was doing, and I then had to go to step 4 again. I also don't have a recovery partition any more.

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Answer 3

Dec 9, 2013 10:35 AM in response to ihaveaposse

Like I said your machine may have the recovery partition in firmware and using the CMD+R key at boot time would get into recovery mode and allow the drive to be wiped and a new copy of Mavericks downloaded from Apple.

Or, thats how I understand it, I don't have a new enough Mac to try it.

Glad you are on your way to fixing it.

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Answer 4

ihaveaposse Author

Level 1

21 points

Dec 9, 2013 10:37 AM in response to rack0 tack0

Sorry I think I neglected to mention I'd booted in recovery mode, since I was wiping the machine for the new owner and you can't do that from within OSX. Just waiting for it to do the free space erasing, then I'll see whether this has solved it. Hopefully will be helpful for someone else.

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