IMac – Is the Fusion Drive set up on the iMac correct? or is there a fix

catalinafusion-driveimacmojave

I have a 2013 iMac previously running Mojave, now running Catalina. I thought on Catalina, that when in Internet Disk Recovery Mode, you should be able to select the Fusion Drive and be able to erase it. However ERASE is greyed out in Disk Utility when I select the Fusion Drive and is not accessible.Is this the way it is suppose to be?

I do have access to erase both the Container, the Macintosh HD and the Macintosh HD – Data, just not the physical drive or "Fusion Drive". Is this iMac still functional and/or is there a way to fix it so the Fusion Drive itself can be erased?

Best Answer

Klanomath and all -

Objective: Properly erase an iMac running Catalina built in 2013

A functional computer should be able to be erased. I was trying to determine the viability of the computer>

Background: I needed to erase my iMac (running Catalina) with a Fusion Drive and was told that ERASE should be accessible while in Disk Utilities in Internet Recovery Mode. ERASE was not accessible on my iMac.

RESOLUTION: My understanding is now that ERASE will NOT be accessible if a Mac has a Fusion Drive and is running Catalina in Disk Utilities in Internet Recovery Mode.

In the end, I could not use Apple's How to erase a disk (https://support.apple.com/en-us/HT208496) documentation, but I can use the directions in Apple's How to split a Fusion Drive (using the Terminal) https://support.apple.com/en-us/HT207584. My understanding is the latter splits or fixes a split, erases and re-fuses the Fusion Drive.

As I can now erase the iMac using the How to split a fusion drive documentation, I have been told the computer is useable.

Side note: I found and so did the people I was working with, the Apple Documentation to be confusing - it can be interpreted in a variety of ways and is not clear with respect to Fusion Drives and how to erase them.

If anyone sees an issue with what I wrote, please feel free to chime in.

Related Solutions

Mac – Can’t delete Logical Volume Group on Fusion drive

If all other means fail to remove a CoreStorage Volume Group you can always use gpt to remove the CS partition (or the CS partitions if it is a Fusion Drive).

Preparation:

Detach your 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 Yosemite or El Capitan) or a thumb drive containing a full system (preferably Yosemite or El Capitan). If you boot to a full system and login as admin you have to prepend sudo to execute some commands like gpt ... or newfs_hfs ...!

Modify the GUID partition table and replace your current LVG

Enter diskutil list and gpt -r show /dev/diskX (with diskX: the disk identifiers of your internal disks (probably disk0 SSD/disk1 HDD) to get an overview. In the commands below I assume the disk identifiers are disk0/disk1.

To delete a partition use:

diskutil umountDisk /dev/disk2 #unmount the Logical Volume(s)
diskutil umountDisk /dev/disk0
diskutil umountDisk /dev/disk1
gpt remove -i index_number /dev/disk0
gpt remove -i index_number /dev/disk1

Usually the Physical Volumes of a Fusion Drive have the index number 2:

gpt remove -i 2 /dev/disk0
gpt remove -i 2 /dev/disk1

Re-add the partitions with the same start block and sizes as they had previously

gpt add -b StartBlock -i 2 -s size -t 48465300-0000-11AA-AA11-00306543ECAC /dev/disk0
gpt add -b StartBlock -i 2 -s size -t 48465300-0000-11AA-AA11-00306543ECAC /dev/disk1

Format the new partition:

newfs_hfs -v "SSD" -J /dev/disk0s2
newfs_hfs -v "HDD" -J /dev/disk1s2

Create a new Logical Volume Group (or "Fusion Drive"):

diskutil cs create name disk0s2 disk1s2 #name: name of the future LVG (e.g. FusinDrive)

Create a new Logical Volume:

diskutil cs list
diskutil cs createVolume lvgUUID jhfs+ name 100% #lvgUUID: the UUID of the Logical Volume Group, name: name of the future LV (e.g. MacintoshHD)

diskutil cs createVolume lvgUUID jhfs+ name size #size in t, g, m (e.g. 3100g)

To quit Terminal enter:
```
exit
```
and quit Terminal
Open Disk Utility to verify the new LVG/LV
Attach the backup drive
Open Time Machine and restore your backup

IMac – Not able to restore the 3TB fusion drive late 2013 iMac

I would suggest following the steps in the answer posted here

Most importantly: diskutil cs create "Macintosh HD" disk0s2 disk1s2

Your diskutil output should look more like this with the "logical volume"

$ diskutil list
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *121.3 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage                         121.0 GB   disk0s2
   3:                 Apple_Boot Boot OS X               134.2 MB   disk0s3
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:          Apple_CoreStorage                         999.3 GB   disk1s2
   3:                 Apple_Boot Recovery HD             650.1 MB   disk1s3
/dev/disk2
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS Macintosh HD           *1.1 TB     disk2
                                 Logical Volume on disk0s2, disk1s2
                                 D11BC089-D75D-4239-AB60-4293803F5F6D
                                 Unencrypted Fusion Drive

And Core Storage list like this:

$ diskutil cs list
CoreStorage logical volume groups (1 found)
|
+-- Logical Volume Group 56F5527E-528E-4FD2-A978-6BDB501423F5
    =========================================================
    Name:         Macintosh HD
    Status:       Online
    Size:         1120333864960 B (1.1 TB)
    Free Space:   0 B (0 B)
    |
    +-< Physical Volume 1CA60BDE-CFCA-414B-A429-B838AD39EA82
    |   ----------------------------------------------------
    |   Index:    0
    |   Disk:     disk0s2
    |   Status:   Online
    |   Size:     120988852224 B (121.0 GB)
    |
    +-< Physical Volume D730D88C-C673-4284-9A91-1B8E705FA5F2
    |   ----------------------------------------------------
    |   Index:    1
    |   Disk:     disk1s2
    |   Status:   Online
    |   Size:     999345012736 B (999.3 GB)
    |
    +-> Logical Volume Family B1CF5519-AC85-4259-9F1F-642EFD4D8B31
        ----------------------------------------------------------
        Encryption Status:       Unlocked
        Encryption Type:         None
        Conversion Status:       NoConversion
        Conversion Direction:    -none-
        Has Encrypted Extents:   No
        Fully Secure:            No
        Passphrase Required:     No
        |
        +-> Logical Volume D11BC089-D75D-4239-AB60-4293803F5F6D
            ---------------------------------------------------
            Disk:                  disk2
            Status:                Online
            Size (Total):          1111826382848 B (1.1 TB)
            Conversion Progress:   -none-
            Revertible:            No
            LV Name:               Macintosh HD
            Volume Name:           Macintosh HD
            Content Hint:          Apple_HFS

Best Answer

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Mac – Can’t delete Logical Volume Group on Fusion drive

IMac – Not able to restore the 3TB fusion drive late 2013 iMac

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