Way to rescue the contents of this messed up Fusion Drive

data-recoveryfusion-drive

I got a Mac in to support with a weird problem with a Fusion Drive. Basically it looks like this

admins-iMac:~ admin$ diskutil corestorage list
CoreStorage logical volume groups (1 found)
|    
+-- Logical Volume Group 31FF02A7-1707-4C28-9FC8-B46D2BA07CF6
    =========================================================
    Name:         Macintosh HD
    Status:       Offline
    Size:         999345012736 B (999.3 GB)
    Free Space:   -none-
    |
    +-< Physical Volume 36937114-03B4-46C5-9D0A-D0106985C1AC
    |   ----------------------------------------------------
    |   (No properties)
    |
    +-< Physical Volume 860ADA37-CD9F-4074-8341-58085C2C6FB5
        ----------------------------------------------------
        Index:    1
        Disk:     disk0s2
        Status:   Checking
        Size:     999345012736 B (999.3 GB)

So the logical drive is the same exact size as one of the physical drives (which I assume is the internal spinning hard drive).
When I open Disk Utility it gives me the "This Fusion Drive is missing a disk" error but the list of disks that will be erased to fix it is empty.

Output from disutil list:

admins-iMac:~ admin$ diskutil list
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage                         999.3 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.1 MB   disk0s3
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *32.0 GB    disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:                  Apple_HFS Yosemite Boot           12.0 GB    disk1s2
   3:                  Apple_HFS Utilities               19.5 GB    disk1s3

I have no idea how it came to this state. Naturally I cannot boot from it and no file rescue software that I have tried will work on it.
Looking at the info for the physical HHD, it doesn't look like it has any file system info on it at all, which doesn't look promising (?):

admins-iMac:~ admin$ diskutil info disk0s2
   Device Identifier:        disk0s2
   Device Node:              /dev/disk0s2
   Part of Whole:            disk0
   Device / Media Name:      iMac HDD

   Volume Name:              Not applicable (no file system)

   Mounted:                  Not applicable (no file system)

   File System:              None

   Partition Type:           Apple_CoreStorage
   OS Can Be Installed:      No
   Recovery Disk:            disk0s3
   Media Type:               Generic
   Protocol:                 SATA
   SMART Status:             Verified
   Disk / Partition UUID:    EAF593A1-5313-4880-9C16-BD20876F969E

   Total Size:               999.3 GB (999345012736 Bytes) (exactly 1951845728 512-Byte-Units)
   Volume Free Space:        Not applicable (no file system)
   Device Block Size:        512 Bytes

   Read-Only Media:          No
   Read-Only Volume:         Not applicable (no file system)
   Ejectable:                No

   Whole:                    No
   Internal:                 Yes
   Solid State:              No

   This disk is a Core Storage Physical Volume (PV).  Core Storage Information:
   PV UUID:                  860ADA37-CD9F-4074-8341-58085C2C6FB5
   LVG UUID:                 31FF02A7-1707-4C28-9FC8-B46D2BA07CF6

First question: If I delete the logical volume with diskutil, the underlying disk(s) should become visible in Disk Utility and otherwise. Is there any chance, seeing as in practise the Fusion Drive only consist of one drive, I will be able to retrieve information from that disk? Either that it will mount normally or I will be able to extract files from it with for instance Data Rescue?

And secondly, is there a chance Disk Utility will be able to actually fix this, if I click the 'Fix' button, and restore the disk with all its contents?

Best Answer

Ok so I did a test before I tried it with the actual affected drive. I had an old 60 GB laptop spinning hard drive, and a 32 GB laptop-form-factor Corsair SSD, which I made into a Fusion Drive. I first formatted each drive and did a secure erase in the process to make sure there were no retrievable files left on the drives. Then used the appropriate diskutil command to make the two into a 92 GB Fusion drive.

Then I copied my 76 GB Photos Library over to this drive, which will make sure there have to be files on both drives. Then left it to "simmer" for a while (i.e. left some time for Core Storage to move files and file blocks around), maybe 1 hour. Then I opened Photos with that library, deleted, duplicated and modified a few photos, maybe 10 or so, over about 15 minutes.

I know this is not a perfect representation of real world usage of a Fusion Drive over a long time, but I feel it would give me a reasonable true idea of the rescue potential of the files in a similar Fusion Drive setup.

Then the test: I properly unmount the Fusion Drive, then plug only the spinning hard drive back in. This replicates the problem with the iMac am I having, where the internal SSD went offline. Now running the diskutil corestorage list command I see the exact same as I did with the iMac: the logical volume is there, but one of the physical disk is listed with no properties to show for it.

I then issue the diskutil cs delete command with the UUID of the logical volume (i.e.the Fusion Drive). It looks like diskutil is formatting the spinning hard drive as a normal HFS+ GUID partition disk, and after it's done the spinning hard drive appears on the desktop, seemingly empty, as you would expect.

Running Disk Rescue 4 on this disk with a Deep Scan shows me the the file rescue potential of this scenario is actually very good. DR4 is able to restore file names and folder structure of approximately 80% of the files and I end of with about 56 GB worth of images.

After this test I basically do the same with the actual iMac that I was tasked with, and I had pretty similar file rescue results with that internal 1 TB spinning hard drive.

Related Solutions

Fusion Drive – Repairing Possible Mess-Up on 1TB iMac with BootCamp

Theoretically everything is fine with your Fusion Drive. Fusion Drives look like this. Disk0 is your SSD with 121 GB and disk1 is your HDD with ~1 TB (~1.121 TB summed up).

The larger parts of your SSD (disk0s2) and your HDD (disk1s2) are pooled to a CoreStorage LVG (Fusion Drive: disk3) with a size of 967.8 GB. The rest is reserved for EFIs, a Recovery HD (alltogether ~1.3 GB) and your old Windows partition - now probably free space (~152 GB).

The logical volume 'Macintosh HD' (967.8 GB) spans disk0s2 and disk1s2. This is the first 'Macintosh HD' in picture 1. The volume 'Macintosh HD' - it's the one visible on the desktop - should ideally also have about 967.8 GB. This is the second 'Macintosh HD' in picture 1.
In fact it has only 852.67 GB (see picture 3).

In the second picture the logical volume 'Macintosh HD' is the first listed in black, the volume 'Macintosh HD' is the second listed in black, the other two 'Macintosh HD's listed in grey are the parts of your SSD and HDD dedicated to the logical volume 'Macintosh HD'.

In my opinion something went wrong after deleting various partitions with the Bootcamp Assistant/Disk Utility or in Windows.

Preparation:

Detach any external drive (especially your external Time Machine backup drive)
Restart to Internet Recovery Mode by pressing alt cmd R at startup.
The prerequisites are the latest firmware update installed, either ethernet or WLAN (WPA/WPA2) and a router with DHCP activated.
On a 50 Mbps-line it takes about 4 min (presenting a small animated globe) to boot into a recovery netboot image which usually is loaded from an apple/akamai server.

I recommend ethernet because it's more reliable. If you are restricted to WIFI and the boot process fails, just restart your Mac until you succeed booting.

Alternatively you may start from a bootable installer thumb drive (preferably Mavericks or Yosemite) or a thumb drive containing a full system (preferably Mavericks or Yosemite).

Now you may either repair CoreStorage or rebuild your Fusion Drive:

'Repair CoreStorage' (not recommended):

First i would try to check the volume 'Macintosh HD' with Disk Utility. If the volume is corrupted consider a reinstall of Mac OS X.
If the volume is ok quit Disk Utility
Open Terminal and enter diskutil unmountDisk /dev/LVIdentifier and both diskutil unmountDisk /dev/DiskContainingApple_CoreStorageIdentifier
In your case: first diskutil unmountDisk /dev/disk3 then diskutil unmountDisk /dev/disk0 and diskutil unmountDisk /dev/disk1
remove the EFI NO NAME partition with gpt remove -i IndexNumberOfEFINoName DiskIdentifier:
gpt remove -i 4 disk1
Remount the CoreStorage disks and then the Logical Volume:
In your case: first diskutil mountDisk /dev/disk0 and diskutil mountDisk /dev/disk1 and then diskutil mount /dev/disk3.

enter gpt -r -vvv show /dev/diskIdentfierOfApple_CoreStorage to get infos of your HDD CoreStorage disk.
In your case: gpt -r -vvv show /dev/disk1
It should look like this:

-bash-3.2# gpt -r -vvv show /dev/disk1
gpt show: /dev/disk1: mediasize=1000204886016; sectorsize=512;         blocks=1953525168
gpt show: /dev/disk1: PMBR at sector 0
gpt show: /dev/disk1: Pri GPT at sector 1
gpt show: /dev/disk1: GPT partition: type=C12A7328-F81F-11D2-BA4B-00A0C93EC93B, start=40, size=409600
gpt show: /dev/disk1: GPT partition: type=53746F72-6167-11AA-AA11-00306543ECAC, start=409640, size=1671210848
gpt show: /dev/disk1: GPT partition: type=426F6F74-0000-11AA-AA11-00306543ECAC, start=1671620488, size=1269760
gpt show: /dev/disk1: Sec GPT at sector 1953525167                               
     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    1671210848      2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC
1671620488       1269760      3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
1672890248     280634887
1953525135            32        Sec GPT table
1953525167             1        Sec GPT header

The free space on your HDD has 280634887 blocks. Please calculate the biggest block number dividable through 8. That's 280634880 blocks (á 512 bytes) which equals 143685058560 B or ~143.7 GB. Add the size of your HDD CoreStorage Physical Volume (852666400768 B) The result is 143685058560 B + 852666400768 B = 996351459328 B
Resize your HDD CoreStorage physical volume with diskutil cs resizeDisk HDDPVUUID newsize
In your case: diskutil cs resizeDisk 93892BE8-2B7F-4ABD-A4C3-984495DCD98D 996351459328b
Calculate the maximal size of your CoreStorage Logical Volume in diskutil cs list: (size disk0s2) + (size disk1s2) In your case that's 120988852224 B + 996351459328 B = 1117340311552 B. That should be the size of your refreshed Logical Volume Group.
Resize your Logical Volume with diskutil cs resizeVolume LVUUID LVGSize-128 MB In your case that's diskutil cs resizeVolume D237FFDC-7DA4-41D7-AC13-4CC7E5E8C0A0 1117212311552b. If you get an error (There is not enough free space...) choose a smaller size like 1117148311552b.
Quit Terminal and open Disk Utility.
Check your expanded CoreStorage Volume for errors.
Quit Disk Utility, choose your CS volume as startup disk and restart your Mac

'Rebuild Fusion Drive' (recommended if you have a Time Machine backup)

Booted to Internet Recovery Mode open Utilities → Terminal in the menubar and enter:
diskutil cs list to get the CoreStorage listing.
Copy the Logical Volume UUID, it's the fifth listed.
Now delete the Logical Volume with diskutil cs deleteVolume LVUUID.
In your case: diskutil cs deleteVolume D237FFDC-7DA4-41D7-AC13-4CC7E5E8C0A0.
Copy the Logical Volume Group UUID, it's the first listed in the listing of diskutil cs list.
Then delete the Logical Volume Group with diskutil cs delete LVGUUID.
In your case: diskutil cs delete 1EFE58BC-3613-44C4-86EE-D816F3B66E3E
Enter exit and quit 'Terminal'
Open 'Disk Utility'. Enter 'Ignore' if you are asked to fix the drives.
Choose your SSD and partition it: 1 Partition Mac OS X Extended (Journaled), hit the Options button and choose GUID Partiton table and hit OK and Apply.
Please check that the size is ~121 GB

Example:
Choose your HDD and partition it: 1 Partition Mac OS X Extended (Journaled), hit the Options button and choose GUID Partiton table and hit OK and Apply.
Please check that the size is ~1 TB

Example:
Quit Disk Utility and open Terminal
Enter diskutil list

Example (your disk identifiers and sizes are different of course: Your volume SSD probably has the Identifier disk0s2 and the size 121 GB and your volume HDD probably has the Identifier disk1s2 and the size 1.0 TB):
Enter diskutil cs create "Name" IdentifierSSD IdentifierHDD
In your case probably diskutil cs create "Macintosh HD" disk0s2 disk1s2.

Copy the resulting LVGUUID

Example:
Enter diskutil cs CreateVolume LVGUUID jhfs+ "Macintosh HD" 100%.

Example:
Enter diskutil cs list
Check the size of your Logical Volume. It should have the size ~1.121 TB

Example:
Quit Terminal
Open 'Disk Utility' and check your newly created volume for errors
Quit 'Disk Utility'
Attach your external Time Machine backup drive or check this answer if you use NAS or another network share.
Open 'Restore from Time Machine Backup'
Choose the appropriate Time Machine backup and restore your system
Reboot to your restored system.
Unmount and detach your Time Machine backup drive
Open 'Terminal' and enter 'diskutil list'
Check if your 'Recovery HD' is listed.
If your 'Recovery HD' is missing, usually reinstalling your current system with the latest available system installer (e.g. 'Install OS X Mavericks (10.9.5)' if Mavericks is currently installed) will recreate it without loosing any data. AFAIK Recovery Partition Creator 3.8 will NOT create a Recovery HD on CoreStorage volumes.
After reinstalling the system with the latest available system installer open App Store and install the latest security fixes.

The full size of the Fusion Drive is not available for repartitioning

Run the following command in Terminal: diskutil cs resizeStack ACA4133B-5F31-4D66-B502-4EABED4E2958 5E6D00FD-4BAD-424C-92CF-F8080CCC2C95 3.128t

The first UUID is your LV UUID, the second is the PV UUID that you want to grow (incase I mistyped one of them).

This will grow your disk back to fill up your 3TB disk. You may have to reduce that number to 3.1279t or something though. 3.128t should work. Unfortunately, you can't specify 100% like you can with many commands.

Best Answer

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Fusion Drive – Repairing Possible Mess-Up on 1TB iMac with BootCamp

The full size of the Fusion Drive is not available for repartitioning

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