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I have a 2017 iMac (version 18,3) with Mojave on a 2TB Fusion Ddrive. The volume is not encrypted, no Bootcamp, I created no extra partitions. Aside from the migrated data from my old MB Pro, it looked like a regular factory installation of Mojave on a Fusion Drive.

While re-compressing some large jpg's, my iMac spontaneously rebooted leaving me with nothing more than the flashing-question-mark-folder icon.

I do have Time Machine but, for various, completely unjustifiable reasons, I have not had TM running for a couple of months. Obviously my fault and intensely stupid. But, since self-recrimination somehow doesn't restore lost data, I have had to resort to other methods.

Long story short involving many spontaneous reboots and kernel panics, The Fusion Drive does not show up as a possible boot drive. Repair is not possible in Disk Utility (First Aid on Apple HDD ST2000DM001 Media (disk0) returns OK. First Aid on APFS Physical Store disk0s2 returns First Aid process has failed. If possible back up the data on this volume.)

I used the internet OS install feature to install Mojave on a Thunderbolt external drive so that I could try to recover data from the dead Fusion Drive. N.B. the system will now boot to the external drive but, even though the external is selected as the boot drive, the system panics at about 60% on the progress bar, spontaneously reboots, then successfully gets to the log in screen on this second go-round. This is consistent behaviour. Once booted, the machine runs normally—perhaps marginally slower as it's off of an external drive.

I installed DDRescue-GUI on the external Thunderbolt drive to image Disk0 to an empty 5TB external drive. This succeeded, returning 0 unreadable data and 0 bad sectors. Well, I think it succeeded. The truth is, I don't really know what a good image of a Fusion Drive constitutes. Noodling around on the internet does not return many positive sounding results.

Might be pertinent: the 2TB image now seems to take up the entire 5TB external drive and in Disk Utility, the drive is listed as uninitialised, 5TB. I'm assuming this is because it's a raw image or something to that effect.

I then installed TestDisk and ran it on the image, I got these results:

First:

    TestDisk 7.1, Data Recovery Utility, July 2019  
    Christophe GRENIER <[email protected]>  
    https://www.cgsecurity.org

    Disk /dev/disk3 - 5000 GB / 4657 GiB - 9767475200 sectors

    The harddisk (5000 GB / 4657 GiB) seems too small! (< 10001 GB / 9314 GiB)
    Check the harddisk size: HD jumper settings, BIOS detection...

    The following partition can't be recovered:
         Partition               Start        End    Size in sectors
      Mac HFS               9767213012 19534016387 9766803376


    [ Continue ]
    HFS+ blocksize=8192, 5000 GB / 4657 GiB

Then, after pressing continue:

Disk /dev/disk3 - 5000 GB / 4657 GiB - 9767475200 sectors
     Partition               Start        End    Size in sectors
>D Mac HFS                   409640 9767213015 9766803376
 D Mac HFS                 91951769   91972248      20480
 D Mac HFS                106597633 1486471047 1379873415 [Dd?2~ET?^B]
 D Mac HFS               2175591462 2175611941      20480
 D Mac HFS               2221847628 2297348942   75501315
 D Mac HFS               2323805053 2525331843  201526791
 D Mac HFS               2529710035 2538099673    8389639 [^A^O~D^T^A]
 D Mac HFS               3140896864 3518384223  377487360
 D Mac HFS               3518384224 3906357343  387973120

Structure: Ok.  Use Up/Down Arrow keys to select partition.
Use Left/Right Arrow keys to CHANGE partition characteristics:
                P=Primary  D=Deleted
Keys A: add partition, L: load backup, T: change type,
     Enter: to continue
HFS+ found using backup sector!, 5000 GB / 4657 GiB

And, since the last line of output is different depending on which partition is selected, here are the other results:

HFS+ blocksize=4096, 10 MB / 10 MiB

HFS blocksize=33554432, 706 GB / 657 GiB

HFS+ blocksize=4096, 10 MB / 10 MiB

HFS blocksize=16777216, 38 GB / 36 GiB

HFS blocksize=16777216, 103 GB / 96 GiB

HFS blocksize=65536, 4295 MB / 4096 MiB

HFS+ blocksize=4096 + Backup, 193 GB / 180 GiB

HFS+ blocksize=4096 + Backup, 198 GB / 185 GiB

I should note that for every partition, it states Structure: Ok.

Before the crash, my drive had roughly 1.3TB of data on it. Looking at those results, things are a bit sliced up.

My question is this: how do I interpret these results and what are my next moves? Imaging the 2TB and scanning for results were fairly time consuming so I'd rather not 'just try something' and have to start over again. While I do have a good image of the bad Fusion Drive (what I think is a good image), if I take the iMac in for service or replacement (it's under warranty) and then also manage to mangle the image, then I'm left with nothing.

I'd like to be able to recover as much as possible before taking the machine in since, no matter how Apple decides to deal with it, I highly doubt that they'll try to recover my data.

Thanks in advance for your time and efforts.

Edit

As requested, I ran diskutil corestorage list.

It returned No CoreStorage logical volume groups found.

Also, if it will help, here is the results of diskutil info disk0, the bad Fusion Drive:

icemo:~ icemo$ diskutil info disk0
   Device Identifier:         disk0
   Device Node:               /dev/disk0
   Whole:                     Yes
   Part of Whole:             disk0
   Device / Media Name:       APPLE HDD ST2000DM001

   Volume Name:               Not applicable (no file system)
   Mounted:                   Not applicable (no file system)
   File System:               None

   Content (IOContent):       GUID_partition_scheme
   OS Can Be Installed:       No
   Media Type:                Generic
   Protocol:                  SATA
   SMART Status:              Verified

   Disk Size:                 2.0 TB (2000398934016 Bytes) (exactly 3907029168 512-Byte-Units)
   Device Block Size:         512 Bytes

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

   Device Location:           Internal
   Removable Media:           Fixed

   Solid State:               No
   Virtual:                   No
   Hardware AES Support:      No

EDIT 24.2.2019 22:03 GMT — added diskutil info for disk0s1 and disk0s2 as they weren't showing up earlier because, I assume, Disk Arbitrator had prevented them from even being attached

For disk0s1:

icemo:~ icemo$ diskutil info disk0s1
   Device Identifier:         disk0s1
   Device Node:               /dev/disk0s1
   Whole:                     No
   Part of Whole:             disk0

   Volume Name:               EFI
   Mounted:                   No

   Partition Type:            EFI
   File System Personality:   MS-DOS FAT32
   Type (Bundle):             msdos
   Name (User Visible):       MS-DOS (FAT32)

   OS Can Be Installed:       No
   Media Type:                Generic
   Protocol:                  SATA
   SMART Status:              Verified
   Volume UUID:               0E239BC6-F960-3107-89CF-1C97F78BB46B
   Disk / Partition UUID:     7A191AE7-EF7C-467B-92B4-152BD8BDB7D7
   Partition Offset:          20480 Bytes (40 512-Byte-Device-Blocks)

   Disk Size:                 209.7 MB (209715200 Bytes) (exactly 409600 512-Byte-Units)
   Device Block Size:         512 Bytes

   Volume Total Space:        0 B (0 Bytes) (exactly 0 512-Byte-Units)
   Volume Free Space:         0 B (0 Bytes) (exactly 0 512-Byte-Units)

   Read-Only Media:           No
   Read-Only Volume:          Not applicable (not mounted)

   Device Location:           Internal
   Removable Media:           Fixed

   Solid State:               No
   Hardware AES Support:      No

For disk0s2:

icemo:~ icemo$ diskutil info disk0s2
   Device Identifier:         disk0s2
   Device Node:               /dev/disk0s2
   Whole:                     No
   Part of Whole:             disk0

   Volume Name:               Not applicable (no file system)
   Mounted:                   Not applicable (no file system)
   File System:               None

   Partition Type:            Apple_APFS
   OS Can Be Installed:       No
   Media Type:                Generic
   Protocol:                  SATA
   SMART Status:              Verified
   Disk / Partition UUID:     EBA70E11-1D8E-41FD-8F4D-73134E713B2C
   Partition Offset:          209735680 Bytes (409640 512-Byte-Device-Blocks)

   Disk Size:                 2.0 TB (2000189177856 Bytes) (exactly 3906619488 512-Byte-Units)
   Device Block Size:         512 Bytes

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

   Device Location:           Internal
   Removable Media:           Fixed

   Solid State:               No
   Hardware AES Support:      No

and for disk3, the image on the external:

icemo:~ icemo$ diskutil info disk3
   Device Identifier:         disk3
   Device Node:               /dev/disk3
   Whole:                     Yes
   Part of Whole:             disk3
   Device / Media Name:       Elements 2620

   Volume Name:               Not applicable (no file system)
   Mounted:                   Not applicable (no file system)
   File System:               None

   Content (IOContent):       None
   OS Can Be Installed:       No
   Media Type:                Generic
   Protocol:                  USB
   SMART Status:              Not Supported

   Disk Size:                 5.0 TB (5000947302400 Bytes) (exactly 9767475200 512-Byte-Units)
   Device Block Size:         512 Bytes

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

   Device Location:           External
   Removable Media:           Fixed

   Virtual:                   No
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  • I'm not sure about the commands you have tried to be honest, but can you run diskutil corestorage list and show us the output? I did a post & answer about a messed up fusion drive here that you can reference: apple.stackexchange.com/questions/290633/… Feb 24, 2020 at 17:18
  • @lars-a-gundersen Thanks for answering, I ran diskutil corestorage list and it returned No CoreStorage logical volume groups found. This does not make me hopeful.
    – tripleman
    Feb 24, 2020 at 18:22

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