Problem factory resetting a new iMac 5K retina with 3 TB fusion drive

Discussion in 'iMac' started by SkotiPati, Jan 26, 2015.

  1. SkotiPati macrumors newbie

    Joined:
    Jan 26, 2015
    #1
    Hello everybody,

    I tried the usual factory reset procedure with my new Mac but have a serious problem with it.

    I used cmd + R, entered disk utility, and tried erasing Macintosh HD but had the "Unable to delete the core storage logical volume" error so I can not reinstall the OS.

    In disk utility I see 2 Macintosh HD one inside the other. They have unusual formats like logical volume group.

    How can I factory reset a new iMac with fusion drive?
     

    Attached Files:

  2. ssls6 macrumors 6502a

    ssls6

    Joined:
    Feb 7, 2013
    #2
    You can only delete the core storage volume (to my knowledge) from the command line. Inside the command shell you basically break the fusion into 2 and then refuse it.

    Did you select the "2nd" Macintosh HD entry and hit "erase"? The one that indented?
     
  3. SkotiPati thread starter macrumors newbie

    Joined:
    Jan 26, 2015
    #3
    Thanks you ssls6,

    Yes I tried the second Macintosh HD and got the error.


    From my further scan through many forums I think I need to do this:

    (please verify these procedures if you can)


    1) Open the computer with "cmd + R"

    2) Open Terminal

    3) diskutil cs delete <Paste UUID of Logical Volume>

    4) diskutil cs delete <Paste UUID of Logical Volume Group>

    5) Go into Disk Utility

    6) Let the Disk Utility fix the Fusion drive from scratch

    7) Reinstall the OS to the new Fusion Drive


    Some web sites only tell me to delete Logical Volume Group but others say that you need to first delete the Logical Volume and then the Logical Volume Group.

    It's all French to me :)

    If someone verifies this action list, I'll do it.


    Thanks.
     
  4. Weaselboy Moderator

    Weaselboy

    Staff Member

    Joined:
    Jan 23, 2005
    Location:
    California
    #4
    Don't worry about the UUID. Just do this to nuke the CS volume. Type it exactly like this including the quotes.

    Code:
    diskutil cs delete "Macintosh HD"
     
  5. SkotiPati, Jan 26, 2015
    Last edited: Jan 26, 2015

    SkotiPati thread starter macrumors newbie

    Joined:
    Jan 26, 2015
    #5
    Are you sure?

    Because there are 2 Macintosh HD originally created by Apple. One has Format of Logical Volume Group, the other Logical Partition.

    With the code you recommend which one will be erased?

    From what I understand you have to delete them in order to completely format both the HD and the SSD of the Fusion drive in iMac. And then let Disk Utility to create a Fusion Drive from 2 empty drives by Fixing.


    thanks weaselboy :)
     

    Attached Files:

  6. Weaselboy Moderator

    Weaselboy

    Staff Member

    Joined:
    Jan 23, 2005
    Location:
    California
    #6
    Yes... trust me, I'm from the Internet. :p

    That is just one hard drive as you know, and it looks that way because of the virtual (logical) drive created by the core storage conversion for Fusion.

    When you run that command they will both be gone and you will be left with the drive itself showing and no formatted partitions.
     
  7. SkotiPati thread starter macrumors newbie

    Joined:
    Jan 26, 2015
    #7
    Thank you Internet! :)

    I'll try and let you know about it.

    Best.
     
  8. SkotiPati thread starter macrumors newbie

    Joined:
    Jan 26, 2015
    #8
    Weaselboy you are my sunshine! :)
    Thanks a lot.

    I think I did it. The only difference from the original Apple structure is there are no longer 2 macintosh HD drives one being the volume geoup the other being the partition.

    Now group is called Internai Drive. Partition is Macintosh HD.

    Also originally disk0 was SSD and disk1 was HD. Now its the reverse.

    I attached the final structure. Is everything ok? I think it is.
     

    Attached Files:

  9. Weaselboy Moderator

    Weaselboy

    Staff Member

    Joined:
    Jan 23, 2005
    Location:
    California
    #9
    Yep... looks like you are in good shape there! :)
     
  10. designbot macrumors newbie

    Joined:
    Aug 3, 2007
  11. auslad88 macrumors newbie

    Joined:
    Mar 16, 2015
    #11
    thanks for this ! This worked for me too - so very grateful! :):cool:
     

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