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Can't mount or reformat drive

macstatic

macstatic

macrumors 68020
Original poster
Oct 21, 2005
2,096
180
Norway
My Mac Pro has several internal drives where one of them is a bootable clone of OSX and my files. I decided to reformat it but it neither mounts on the Finder desktop nor allows me to erase it!
Within Disk Utility the drive does appear with its correct name, but unlike my other drives (all with a single partition), only one icon is show. This is the information Disk Utility gives me about that drive:

Type: Logical Volume Group
Disk Status: Online
Physical backing: disk1s2

If I click on the "First aid" tab I can verify or repair the disk. Either tells me that "the disk appears to be OK". The "Partition" tab doesn't allow me to do anything as it's all greyed out. The "Erase", "RAID" and "Restore" tabs for this drive are completely gone.
Is my drive "bricked" or is there a way to make it work again?

PS: I tried using the fcsk_hfs command as explained here but it didn't help.
 
Last edited:
Type: Logical Volume Group
Click to expand...

Here is what's up. That drive is either encrypted with FileVault or has been converted into a core storage volume, and that is preventing you from working with it.

Run the command below in Terminal then post the output here and I can tell you how to wipe the drive.

Code: 
diskutil cs list
 
Sure, here's what it says:

Code: 
$ diskutil cs list
CoreStorage logical volume groups (1 found)
|
+-- Logical Volume Group 586B6CDA-A819-4925-8937-05B96B39044F
    =========================================================
    Name:         Emergency backup
    Status:       Online
    Size:         3000249008128 B (3.0 TB)
    Free Space:   2999913455616 B (3.0 TB)
    |
    +-< Physical Volume 308BB3E3-B5FA-4EE6-8D6F-8341DBE6CCEB
        ----------------------------------------------------
        Index:    0
        Disk:     disk1s2
        Status:   Online
        Size:     3000249008128 B (3.0 TB)

I've never used Filevault, so that can't be it.
And according to what I've read in various other forums or websites I've also tried entering this command " fdisk -e /dev/disk1s2" as well as "fsck -yf" in addition to what I linked to but this hasn't changed anything.
 
macstatic said:
Sure, here's what it says:

I've never used Filevault, so that can't be it.
And according to what I've read in various other forums or websites I've also tried entering this command " fdisk -e /dev/disk1s2" as well as "fsck -yf" in addition to what I linked to but this hasn't changed anything.
Click to expand...

That volume somehow got converted to a core storage volume and that's the problem. May have happened if you did a Yosemite upgrade.

Just enter the command below in Terminal and it will kill the core storage volume, then you can format normally. Make sure to enter it exactly like this including the quotes.

Code: 
diskutil cs delete "Emergency backup"
 
That solved my problem! Thank you!!! :)

EDIT: there's something strange going on here.....
After issuing the "cs delete...." command all looks fine and normal in Disk Utility, but if I erase it again it switches back to Core storage, and once again the drive only gets to have the "First Aid" and "Partition" tabs in Disk Utility. And if I erase the drive it gets the same name in both the drive and partition.

UPDATE: I read a suggestion somewhere to boot with an OSX installation DVD and erase the drive with Disk utility from there, so I booted with my OSX 10.6 Snow Leopard DVD and it formatted the drive just as it should -all problems solved!
So next I rebooted back into 10.9.5. and just to ensure the drive was OK I erased the drive once again in Disk Utility, but just like before it got converted into a Core Storage drive (it says Switching disk1s2 to Core Storage and Discovered new Logical Volume Group "xxxxx xx xx x xxxxxx"). Seems like my OSX 10.9.5. recognizes the drive and tells it to become a Core Storage drive yet again.
 
Last edited:
macstatic said:
… 10.9.5 … erased the drive … Disk Utility … Switching disk1s2 to Core Storage …
Click to expand...

For me with Mavericks, at a glance the last switch was probably in September 2014, and the switch was expected. Log extract below.

macstatic, please: what's in the following log files from the time of the unexpected switch?

~/Library/Logs/DiskUtility.log

/var/log/system.log


Code: 
**********
2014-09-21 15:29:16 +0100: Disk Utility started.

2014-09-21 15:31:28 +0100: Preparing to partition disk: “Kingston DataTraveler G3 Media”
2014-09-21 15:31:28 +0100: 	Partition Scheme: GUID Partition Table
2014-09-21 15:31:28 +0100: 	2 partitions will be created
2014-09-21 15:31:28 +0100: 
2014-09-21 15:31:28 +0100: 	Partition 1
2014-09-21 15:31:28 +0100: 		Name		: “Untitled 1”
2014-09-21 15:31:28 +0100: 		Size		: 2 GB
2014-09-21 15:31:28 +0100: 		Requested	: 2.14 GB
2014-09-21 15:31:28 +0100: 		Estimated Start Loc	: 0
2014-09-21 15:31:28 +0100: 		File system	: Mac OS Extended (Journaled)
2014-09-21 15:31:28 +0100: 		Partition does not already exist
2014-09-21 15:31:28 +0100: 		Contents will be erased
2014-09-21 15:31:28 +0100: 
2014-09-21 15:31:28 +0100: 	Partition 2
2014-09-21 15:31:28 +0100: 		Name		: “Untitled 2”
2014-09-21 15:31:28 +0100: 		Size		: 2 GB
2014-09-21 15:31:28 +0100: 		Requested	: 2.14 GB
2014-09-21 15:31:28 +0100: 		Estimated Start Loc	: 2,139,095,040
2014-09-21 15:31:28 +0100: 		File system	: Mac OS Extended (Journaled)
2014-09-21 15:31:28 +0100: 		Partition does not already exist
2014-09-21 15:31:28 +0100: 		Contents will be erased
2014-09-21 15:31:28 +0100: 
2014-09-21 15:31:29 +0100: Unmounting disk
2014-09-21 15:31:45 +0100: Creating the partition map
2014-09-21 15:31:54 +0100: Waiting for the disks to reappear
2014-09-21 15:31:54 +0100: Formatting disk12s2 as Mac OS Extended (Journaled) with name Untitled 1
2014-09-21 15:32:10 +0100: Initialized /dev/rdisk12s2 as a 2 GB case-insensitive HFS Plus volume with a 8192k journal

2014-09-21 15:32:10 +0100: Mounting disk
2014-09-21 15:32:10 +0100: Formatting disk12s3 as Mac OS Extended (Journaled) with name Untitled 2
2014-09-21 15:32:36 +0100: Initialized /dev/rdisk12s3 as a 1 GB case-insensitive HFS Plus volume with a 8192k journal

2014-09-21 15:32:36 +0100: Mounting disk
2014-09-21 15:32:51 +0100: Partition complete.
2014-09-21 15:32:51 +0100: 
updateDMList for list containing 8 items
Starting next Erase job: 7 with options: {
    AKSPassphraseUUID = "24E35613-6477-4D9E-A55B-52E62671CF92";
    pFilesystemName = "Journaled HFS+";
    pVolName = "journaled, encrypted";
}
2014-09-21 15:33:32 +0100: Unmounting disk12s2
2014-09-21 15:33:43 +0100: Touching partition type on disk12s2
2014-09-21 15:33:56 +0100: Adding disk12s2 to Logical Volume Group
2014-09-21 15:33:56 +0100: Creating Core Storage Logical Volume Group
2014-09-21 15:34:03 +0100: Switching disk12s2 to Core Storage
updateDMList for list containing 8 items
2014-09-21 15:35:32 +0100: Waiting for Logical Volume Group to appear
2014-09-21 15:35:32 +0100: Discovered new Logical Volume Group “391198AA-F179-466A-BD30-1B9BF02D9CAF”
Starting next Erase job: 8 with options: {
    AKSPassphraseUUID = "24E35613-6477-4D9E-A55B-52E62671CF92";
    LVGUUID = "391198AA-F179-466A-BD30-1B9BF02D9CAF";
    pFilesystemName = "Journaled HFS+";
    pVolName = "journaled, encrypted";
}
2014-09-21 15:35:36 +0100: Waiting for Logical Volume to appear
2014-09-21 15:35:40 +0100: Formatting file system for Logical Volume
2014-09-21 15:35:57 +0100: Initialized /dev/rdisk13 as a 2 GB case-insensitive HFS Plus volume with a 8192k journal

2014-09-21 15:35:57 +0100: Mounting disk
2014-09-21 15:35:58 +0100: Erase complete.
2014-09-21 15:35:58 +0100: 
Starting next Erase job: 7 with options: {
    AKSPassphraseUUID = "12292F08-CE1C-497D-A173-FAEA2A9B0259";
    pFilesystemName = "Case-sensitive Journaled HFS+";
    pVolName = "case-sensitive, journaled, encrypted";
}
2014-09-21 15:42:26 +0100: Unmounting disk12s3
2014-09-21 15:42:37 +0100: Touching partition type on disk12s3
2014-09-21 15:42:51 +0100: Adding disk12s3 to Logical Volume Group
2014-09-21 15:42:51 +0100: Creating Core Storage Logical Volume Group
2014-09-21 15:42:58 +0100: Switching disk12s3 to Core Storage
updateDMList for list containing 8 items
2014-09-21 15:44:29 +0100: Waiting for Logical Volume Group to appear
2014-09-21 15:44:29 +0100: Discovered new Logical Volume Group “CA81191D-B39E-4B19-B4B6-FEC1FF3D2478”
Starting next Erase job: 8 with options: {
    AKSPassphraseUUID = "12292F08-CE1C-497D-A173-FAEA2A9B0259";
    LVGUUID = "CA81191D-B39E-4B19-B4B6-FEC1FF3D2478";
    pFilesystemName = "Case-sensitive Journaled HFS+";
    pVolName = "case-sensitive, journaled, encrypted";
}
2014-09-21 15:44:32 +0100: Waiting for Logical Volume to appear
2014-09-21 15:44:37 +0100: Formatting file system for Logical Volume
2014-09-21 15:44:53 +0100: Initialized /dev/rdisk14 as a 1 GB case-sensitive HFS Plus volume with a 8192k journal

2014-09-21 15:44:53 +0100: Mounting disk
2014-09-21 15:44:54 +0100: Erase complete.
2014-09-21 15:44:54 +0100: 
**********
 
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