Fusion Drive not bootable or mountable, although First Aid shows fine

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Level 1

4 points

Fusion Drive not bootable or mountable, although First Aid shows fine

My late-2014 iMac is refusing to boot in any manner except Safe Mode.

When I run Disk Utility, I see the "Internal" drive and the "Macintosh HD" volume: both check out okay if I run First Aid on them. However, as you can see on the attached screen shot: it shows as having 0 space and being entirely consumed with "other" files and is listed as neither bootable nor writable ⚠.

When I click "mount" nothing happens.

When I try to either restore from my Time Machine backup or re-install OS X, the drive does not appear as an option.

It appears to me that my next step would be to try to erase the drive and then restore, but naturally I'm nervous about making a non-reversible decision.

My specific question is whether Disk Utility is "telling the truth" when it says there is zero space on the drive and it's non-writable. Or is this there another computer / drive state that could cause this appearance?

Assuming it *is* telling the truth, is "Erase the disk" likely to work or will I likely have to reformat / repartition the drive? (Which is also nervous-making, since it's a Fusion drive, and I know that can be tricky.)

Mac OS X (10.6.4)

Posted on Jan 24, 2016 10:15 AM

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Answer 1

KonaKoder Author

Level 1

4 points

Jan 24, 2016 11:05 AM in response to KonaKoder

Further investigation makes it seem like:

I filled up my hard drive (probably my video-editing yesterday);
When OS X boots, it sees 0 free blocks and switches the drive to be write-only
I can't overcome this, even in single-user mode

I would really prefer to somehow force deletion of stuff in /.Trashes and /Downloads before erasing the whole drive and hoping my Time Machine works out.

Any ideas?

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Answer 2

KonaKoder Author

Level 1

4 points

Jan 25, 2016 10:43 AM in response to KonaKoder

Ultimately, I was able to:

Boot with Internet Recovery: (alt-cmd-R)
In Terminal, use `diskUtil erase` to delete the Fusion drive logical volume
Run Disk Utility, which diagnosed the Fusion drive and prompted me to repair it, effectively re-setting the partition and data on the drive
Restore from Time Machine

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Answer 3

Kappy

Level 10

362,007 points

Jan 24, 2016 10:24 AM in response to KonaKoder

First, are you actually able to boot the computer as-is? If so, then there is nothing wrong, and you don't understand about Core Storage managed disks. Or the disk is actually messed up since it appears it is not mounted.

If you want to reformat/erase the volume, then click on the Erase tab in the toolbar.

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Answer 4

Kappy

Level 10

362,007 points

Jan 24, 2016 11:30 AM in response to KonaKoder

No, if the drive is literally full, then the drive is useless. You might try backing up data while in Safe Mode, but I suspect that will fail. You have only one solution:

Install or Reinstall OS X from Scratch

Be sure you have backed up your files because the following procedure will remove everything from the hard drive.

Boot to the Recovery HD:

Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears.

Erase the hard drive:

1. Select Disk Utility from the main menu and click on the Continue button.

2. After DU loads select your startup volume (usually Macintosh HD) from the

left side list. Click on the Erase tab in the DU main window.

3. Set the format type to Mac OS Extended (Journaled.) Optionally, click on

the Security button and set the Zero Data option to one-pass. Click on

the Erase button and wait until the process has completed.

4. Quit DU and return to the main menu.

Reinstall OS X: Select Reinstall OS X and click on the Install button.

Note: You will need an active Internet connection. I suggest using Ethernet if possible

because it is three times faster than wireless.

This should install the version of OS X that you had installed.

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Answer 5

KonaKoder Author

Level 1

4 points

Jan 24, 2016 11:45 AM in response to Kappy

Neither "Erase" nor even "Partition" in Disk Util work. Can I erase and/or partition the drive from the command-line somehow?

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Answer 6

Kappy

Level 10

362,007 points

Jan 24, 2016 11:48 AM in response to KonaKoder

Are you trying this after booting to the Recovery HD? If so, then I can only suggest you try booting from another drive such as an external clone if you have one. Beyond that I'd guess the drive is failing or has failed.

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Answer 7

KonaKoder Author

Level 1

4 points

Jan 24, 2016 11:07 AM in response to Kappy

I can boot into Recovery and Single-User mode, but I cannot boot to the Desktop mode in any manner.

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