IMac – How to re-fuse an unfused Fusion Drive, ideally without formatting

core-storagefusion-driveimacssd

I have a 5k iMac with a Fusion Drive. I had trouble with macOS, so I reinstalled it, and restored from a Time Machine backup using Migration Assistant.

After that, the system has been very slow, and beachballs all the time. Looking in Disk Utility, I find that the Fusion Drive was destroyed:

Notice that Macintosh HD is within the HDD, and the SSD is unformatted.

Here's the output of diskutil cs list. It seems that there's already a Core Storage logical volume group, but it's too small (121GB rather than 2.1TB):

CoreStorage logical volume groups (1 found)
|
+-- Logical Volume Group 7090C28E-A2D2-49C3-BDA4-0B4C96F499B4
    =========================================================
    Name:         Macintosh HD
    Status:       Offline
    Size:         120988852224 B (121.0 GB)
    Free Space:   -none-
    |
    +-< Physical Volume E8FF728C-B2AD-44F5-B9B9-EE0BE22D1782
    |   ----------------------------------------------------
    |   Index:    0
    |   Disk:     disk0s2
    |   Status:   Checking
    |   Size:     120988852224 B (121.0 GB)
    |
    +-< Physical Volume FCB9BDAF-B3E1-403D-B078-CD967BEDECB3
        ----------------------------------------------------
        (No properties)

And here's the partition map. Strangely, I have Macintosh HD and EFI partitions on both disks:

$ diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *121.3 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage Macintosh HD            121.0 GB   disk0s2
   3:                 Apple_Boot Boot OS X               134.2 MB   disk0s3

/dev/disk1 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *2.0 TB     disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:                  Apple_HFS Macintosh HD            2.0 TB     disk1s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk1s3

And here's more detailed info about the HDD:

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

   Volume Name:              Macintosh HD
   Mounted:                  Yes
   Mount Point:              /

   Partition Type:           Apple_HFS
   File System Personality:  Journaled HFS+
   Type (Bundle):            hfs
   Name (User Visible):      Mac OS Extended (Journaled)
   Journal:                  Journal size 155648 KB at offset 0x3a38000
   Owners:                   Enabled

   OS Can Be Installed:      Yes
   Recovery Disk:            disk0s3
   Media Type:               Generic
   Protocol:                 SATA
   SMART Status:             Verified
   Volume UUID:              388929F6-08C6-31FF-9AB1-3AB0E5FF1383
   Disk / Partition UUID:    D3F0C33F-6052-46F9-A4BE-90D4435B183A

   Disk Size:                2.0 TB (1999404957696 Bytes) (exactly 3905087808 512-Byte-Units)
   Device Block Size:        512 Bytes

   Volume Total Space:       2.0 TB (1999404957696 Bytes) (exactly 3905087808 512-Byte-Units)
   Volume Used Space:        1.3 TB (1325673127936 Bytes) (exactly 2589205328 512-Byte-Units) (66.3%)
   Volume Available Space:   673.7 GB (673731829760 Bytes) (exactly 1315882480 512-Byte-Units) (33.7%)
   Allocation Block Size:    4096 Bytes

   Read-Only Media:          No
   Read-Only Volume:         No

   Device Location:          Internal
   Removable Media:          Fixed

   Solid State:              No

And the SSD:

$ diskutil info /dev/disk1s2
   Device Identifier:        disk1s2
   Device Node:              /dev/disk1s2
   Whole:                    No
   Part of Whole:            disk1

   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
   Media Type:               Generic
   Protocol:                 PCI
   SMART Status:             Verified
   Disk / Partition UUID:    0993633C-EC5D-473D-AC5A-8CB967E9D532

   Disk Size:                121.0 GB (120988852224 Bytes) (exactly 236306352 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:              Yes
   Device Location:          "SSD"

   This disk is a Core Storage Physical Volume (PV).  Core Storage Information:
   PV UUID:                  E8FF728C-B2AD-44F5-B9B9-EE0BE22D1782
   LVG UUID:                 7090C28E-A2D2-49C3-BDA4-0B4C96F499B4

diskutil repairDisk works for the HDD (disk0), and doesn't seem to find much to repair. But it flags an error on the SSD (disk1):

$ sudo diskutil repairDisk /dev/disk1
[...]
Logical Volume Group 7090C28E-A2D2-49C3-BDA4-0B4C96F499B4 spans 2 devices
Incomplete or inconsistent CoreStorage Physical Volume set
Storage system check exit code is 1
Problems were encountered during repair of the partition map
Error: -69716: Storage system verify or repair failed
Underlying error: 1: Operation not permitted

When I run
fsck_cs /dev/disk0, it says that it's not a CoreStorage volume, and likewise for disk1.

Has the Fusion Drive become unfused? How do I re-fuse it?

Ideally without formatting or reinstalling macOS? I'll backup just in case, but I hope not to use it.

I looked at diskutil mergePartitions ..., but it seems to work only for partitions on the same physical disk. Is there another way?

Ideally using free software, but I'm willing to pay if needed.

This is on Sierra, 10.12.1.

Best Answer

If your disks or volumes don't have a second problem the following steps should work:

Backup your main system volume
Boot to Recovery Mode
Open in the menubar Utilities > Terminal
Get an overview with diskutil list and diskutil cs list
Below I assume the SSD is disk0 and the HDD disk1 (compare the sizes)
Check all important volumes and drives with diskutil verifyDisk diskX and diskutil verifyVolume diskXsY. If necessary repair the disks and volumes.
Revert the CoreStorage LVG (SSD) to a normal partition setup:
```
diskutil cs revert lvUUID
```
This may fail because an lvUUID doesn't exit - then you have to try to delete the Logical Volume Group.
```
diskutil cs delete lvgUUID
```
This may fail also - then you have to "hard-reset" the SSD's partition table by repartitioning it. Finally check with diskutil cs list that no Logical Volume Group exists.
Convert your main system volume (disk1s2) to a CS Logical Volume Group:
```
diskutil cs convert disk1s2
```
Your data will be preserved. This will assign new UUIDs to the (new) LVG, PV, LVF and the LV.
Add disk0s2 as a Physical Volume to the LVG:
```
diskutil cs addDisk lvgUUID disk0s2
```
Resize the Logical Volume with:
```
diskutil cs resizeVolume lvUUID 0g
```
Reboot

with lvUUID = UUID of a Logical Volume; lvgUUID = UUID of a Logical Volume Group. The command diskutil cs addDisk ... is undocumented but works in Sierra.

The approach may fail because other (unknown) obstacles exist. In my VM it worked.

Related Solutions

MacOS – Unable to reformat/repartition CoreStorage logical volume (Fusion drive)

I was able to delete a mess I made trying to delete my Raid 10 in diskutil (which ended up looking similar to above) using the commands below in Terminal.app. May or may not work with fusion but it's easier than booting up again.

Get rid of the volume - copy paste the logical volume name where it says "Logical Volume Name", without the quotes:

diskutil cs deleteVolume "*Logical Volume Name*"

Free the disk - copy paste the volume name where it says "Physical Volume Name", without the quotes:

diskutil cs removeDisk "*Physical Volume name*"

Repeat these steps as needed.

I think I messed up the Fusion Drive on the 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.

Best Answer

Related Solutions

MacOS – Unable to reformat/repartition CoreStorage logical volume (Fusion drive)

I think I messed up the Fusion Drive on the 1TB iMac (with BootCamp)

Related Question