Can't remove Core Storage from hard drive

Question

Level 1

9 points

Can't remove Core Storage from hard drive

I wanted to erase a backup drive and start over again but somehow it's gotten converted to "Core Storage" I'm told.

I managed to erase the drive by first listing the Core Storage devices, using the following command in the OSX Terminal:

diskutil cs list

Then erasing the drive:

diskutil cs delete "Backup2"

This made everything look OK in Disk Utility, because now the drive appears as having a volume in addition to the drive icon, and there are also 4 tabs available (First Aid, Erase, Partition, RAID, Restore), but if I erase the drive something strange happens: it says "Switching disk1s1 to Core Storage", and after that the two drive icons in Disk Utility get the same name (all my other drives show an icon with the drive brand/model while the second icon shows the volume name). And the main drive icon only has 2 options now: First Aid and Partition. The volume icon has 3 options in DIsk Utility: First Aid, Erase, Restore.

The obvious thing to do at this stage is select "Erase", but this only results in the volume icon changing its name separately from the drive itself.

I've also tried booting with my OSX 10.6 installation DVD and erasing the drive from there, but the result is the same when I try to erase it once again. Seems like my OSX has somehow decided that this specific drive must be a Core Storage device regardless of what I've done to the actual drive itself.

What do I need to do in order to make the drive "normal" again? I'm using OSX 10.9.5.

Mac Pro, OS X Mavericks (10.9.5)

Posted on Mar 31, 2015 10:27 AM

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Answer 1

Kappy

Level 10

361,741 points

Mar 31, 2015 10:34 AM in response to osmanthus

You need to repartition the entire drive, not just erase the volume.

Clean Install of Snow Leopard

Be sure to make a backup first because the following procedure will erase

the drive and everything on it.

1. Boot the computer using the Snow Leopard Installer Disc or the Disc 1 that came

with your computer. Insert the disc into the optical drive and restart the computer.

After the chime press and hold down the "C" key. Release the key when you see

a small spinning gear appear below the dark gray Apple logo.

2. After the installer loads select your language and click on the Continue

button. When the menu bar appears select Disk Utility from the Utilities menu.

After DU loads select the hard drive entry from the left side list (mfgr.'s ID and drive

size.) Click on the Partition tab in the DU main window. Set the number of

partitions to one (1) from the Partitions drop down menu, click on Options button

and select GUID, click on OK, then set the format type to MacOS Extended

(Journaled, if supported), then click on the Apply button.

3. When the formatting has completed quit DU and return to the installer. Proceed

with the OS X installation and follow the directions included with the installer.

4. When the installation has completed your computer will Restart into the Setup

Assistant. After you finish Setup Assistant will complete the installation after which

you will be running a fresh install of OS X. You can now begin the update process

by opening Software Update and installing all recommended updates to bring your

installation current.

Download and install Mac OS X 10.6.8 Update Combo v1.1. You can download Yosemite from the App Store and upgrade. Note, that Yosemite creates a CoreStorage volume automatically. If you wish to revert it back to HFS+, then you need to use a different Terminal command than what you did before: sudo diskutil cs revert ..... You need to look at the man pages for this to know what comes after "revert."

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Answer 2

keg55

Level 6

11,743 points

Mar 31, 2015 11:26 AM in response to osmanthus

Using Terminal, try the following two CoreStorage commands.

First you need to get the Logical Volume Group's identifier (LVG UUID). So, type diskutil cs list. Look at the 1st line for Logical Volume Group and copy the string of letters/numbers/dashes. Next, type diskutil cs delete <LVG UUID> and paste the string of characters after delete. This should delete the CoreStorage volume so you can partition and format your drive.

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Answer 3

osmanthus Author

Level 1

9 points

Mar 31, 2015 2:56 PM in response to Kappy

Kappy: thanks, but I have to explain that I'm not in the process of upgrading from OSX 10.6 Snow Leopard (I grabbed the OSX 10.6 installation DVD because it allows me to boot from another media than the computer's boot drive -Mavericks doesn't come on a DVD of course and I haven't taken the time to figure out how to install it on a USB thumb drive).

I actually did a clean install (backup everything, reformat the drive, install OSX from scratch) of OSX 10.9 Mavericks recently, and the reason for reformatting the problematic drive in the first place was to do a completely new backup since I don't want to risk keeping keep bits of 10.6 mixed in there with 10.9.

I somehow messed up the drive which made it Core Storage and now it refuses to act as a normal drive.

My Mac consists of several drives where the abovementioned drive acts as a bootable backup.

Keg55: Thanks for your suggestions but I'm still running into the same issue as before: after doing the terminal commands my drive seems fine, but when I open Disk Utility (DU) and format ("erase") the drive gets converted back into Core Storage. I erase it in order to test if things have really gotten back to normal or if the Core Storage thingy still sticks with my system somehow (which it does). I'd never even heard of Core Storage until now (and still don't understand what it really is as most of the documentation I've found is highly technical), but could it be that OSX 10.9 Mavericks is supposed to do this while 10.6 Snow Leopard isn't (hence what Kappy is saying in the last part of the reply above about Yosemite creating Core Storage volumes automatically? Is this what applies here, or have I misunderstood?

OK, let me explain what happens step by step... The goal of course is to format the drive so as to act as a normal "Mac OS extended (journaled)" drive (as I said I don't even know what Core Storage is and don't know why I would be wanting this), so here goes....

1) At the first stage I have the drive freshly deleted using the diskutil cs delete LVG_UUID command (diskutil cs delete "volume_group_name" appears to be doing the same thing), so it's just like my other drives as far as I can see in DU (showing the drive brand/model and a partition icon underneath as seen in the screenshot below).

2) Now I want to verify if my drive has really become "normal" again or if it acts up once more by becoming a Core Storage drive again.

I click on the drive's (not its partition) icon in DU, select the "Erase" tab and finally press the erase button.

3) After pressing the erase button, messages pop up at the bottom part of DU very quickly. Luckily I can do screenshots faster than I can read, so here's what I've captured DU telling me. First it's converting the drive to Core Storage:

4) next it switching the drive to Core storage:

5) and finally it's formatting the file system for logical volume (whatever that means):

and as you can see in the top left corner the drive now only shows a single icon (unlike every time I've formatted a drive in the past it shows the drive and a partition icon, where the drive icon is followed by the drive's brand/model name).

So what's going on here and why can't I get my drive back to normal when erasing it?

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Answer 4

keg55

Level 6

11,743 points

Mar 31, 2015 3:45 PM in response to osmanthus

All I can think of is it has something to do with a 3TB partition on WD drives. Have you tried splitting the drive into 2 or 3 partitions and then try to erase/format each partition? You will have to do the diskutil cs delete <LVG> Terminal command again to start over. If you're successful, I don't know what you would need to do to merge the partitions back into one.

For what it's worth, having a CoreStorage volume is not a bad thing other than only being able to create one additional partition. So, unless you need to split that drive out, you're ok with leaving it as a CoreStorage volume.

Do some Google searches to find out if there are any solutions out there.

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Answer 5

osmanthus Author

Level 1

9 points

Apr 1, 2015 3:38 PM in response to keg55

Interesting stuff which I had to try....

So after issuing the terminal command "diskutil cs delete LVG_UUID" and entering Disk Utility I found out that the key is to select the "Partition" tab instead of "Erase". By choosing to partition the drive (regardless of 1,2,3 or 4 partitions which I tried) everything worked perfectly, as before! I was left with a standard MacOS extended (journaled) drive.

But if I chose to "erase" the drive the Core Storage thing appeared again.

My preliminary conclusion (based on these findings and what Kappy said about Yosemite creating Core Storage volumes automatically) is that this is a Mavericks thing (I read that Core Storage came with OSX 10.7 Lion) and not present in 10.6 Snow Leopard, and that formatting the same drive the same way I did before in the same application (Disk Utility) now yields different results. Kappy, can you confirm this?

I don't understand the complicated explanations of what Core Storage is, but since I don't want to risk messing things up even more I think I'll just stick with having the drive HFS formatted/partitioned as I had it under OSX 10.6.

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Answer 6

osmanthus Author

Level 1

9 points

Apr 1, 2015 3:58 PM in response to osmanthus

By the way, why am I asked for my admin password twice when doing a drive "Erase" in DU? I understand that the system wants to ensure I'm not going to format a drive by mistake, but the second time? If I press the "Cancel" button I'm told this (which seems very strange since I haven't tried to encrypt any of my drives):

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Answer 7

ivan_e

Level 1

0 points

Jun 17, 2015 5:35 PM in response to osmanthus

i suggest you first delete the core storage logical volume group via terminal:

diskutil cs list --> find LVG UID (on first line, very long number string)

diskutil cs delete <<LVG UID>>

then format the disk also via terminal:

diskutil list --> find the disk number (like "disk2") of the disk you want to format

diskutil erasedisk JHFS+ untitled /dev/disk(number of the disk)

this worked just fine for me

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