Corrupt iMac Fusion drive?

davidlv

macrumors 65816
Original poster
Apr 5, 2009
1,260
22
Kyoto, Japan
Inherited an iMac 13,2 (late 2012 model) with a fusion drive 128GB SSD + 1TB HD)
Booted up from an external USB disk, and using terminal, typed in "diskutil cs list" and got a message saying "No CoreStorage logical volume groups found" rather than the expected fusion logical volume ID and the coreStorage logical volume group ID.
I want to delete the fusion drive and split the SSD and HD.
Any suggestions?
 

nambuccaheadsau

macrumors 68000
Oct 19, 2007
1,788
417
Nambucca Heads Australia
Helps if you provide full information. Is the hard drive formatted APFFS for Mojave/Catalina? If so go this way, different operation to Journaled Extended formatting, known as HFS+:-



For HFS+ drives follow these directions:-

 

davidlv

macrumors 65816
Original poster
Apr 5, 2009
1,260
22
Kyoto, Japan
Now I am booted up from an external USB drive (/dev/disk3 Apple_HFS Plex M5S in the list below) running Mojave 10.14.6
Here is a list of the drives. I used both of the following commands from terminal; diskutil cs list and diskutil coreStorage list, but both say "No CoreStorage logical volume groups found".
I also tried booting up from an Internet Recovery partition (Option Command r) but got the same result from Terminal. I also have an APFS formatted external SSD in a USB case, so Iguess I could try booting from that drive (probably will report the same result as the Mac HD fusion drive is the same).

davidv$ 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_APFS Container disk2 121.1 GB disk0s2

/dev/disk1 (internal, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *1.0 TB disk1
1: EFI EFI 209.7 MB disk1s1
2: Apple_APFS Container disk2 1000.0 GB disk1s2

/dev/disk2 (synthesized):
#: TYPE NAME SIZE IDENTIFIER
0: APFS Container Scheme - +1.1 TB disk2
Physical Stores disk0s2, disk1s2
1: APFS Volume Preboot 21.2 MB disk2s2
2: APFS Volume Recovery 516.6 MB disk2s3
3: APFS Volume VM 1.1 GB disk2s4
4: APFS Volume Mac HD 55.5 GB disk2s1

/dev/disk3 (external, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *256.1 GB disk3
1: EFI EFI 209.7 MB disk3s1
2: Apple_HFS Plex M5S 255.2 GB disk3s2
3: Apple_Boot Recovery HD 650.0 MB disk3s3
 
Last edited:

nambuccaheadsau

macrumors 68000
Oct 19, 2007
1,788
417
Nambucca Heads Australia
You will be able to boot into Recovery7 from there go to utilities in the Menu Bar and access Terminal from there. Select the first option I posted. Here is how to do this, about half way down nthe page:-


Terminal and use the commands as appears
 

davidlv

macrumors 65816
Original poster
Apr 5, 2009
1,260
22
Kyoto, Japan
You will be able to boot into Recovery7 from there go to utilities in the Menu Bar and access Terminal from there. Select the first option I posted. Here is how to do this, about half way down nthe page:-


Terminal and use the commands as appears
Thanks for the reply and trying to help. Unfortunately, that does not work. I have tried twice, once booted into the regular recovery partition and once booted into the Internet Recovery Partition. Using terminal, typed in "diskutil CoreStorage list" and got a message saying "No CoreStorage logical volume groups found" rather than the expected fusion logical volume ID and the coreStorage logical volume group ID. (tried "diskutil cs list" also, same result) I know it is functioning as a Fusion drive, there is about 1.1TB of storage available
I found another post (https://forums.macrumors.com/threads/fusion-drive-no-corestorage-logical-volume-groups-found.2161592/) that says:
"If you're installed Mojave (10.14.2 or later), your Fusion drive has been converted to APFS, hence, no CoreStorage. Which is why you're receiving that return message from Terminal." ie. that message is not a problem as I thought it was.
Post what you get from 'diskutil apfs list'. What you can do is just find the bsd names, likely disk0 and disk1, and unmount them with 'diskutil unmountdisk force disk0' and the same thing for disk1, then erase them individually in terminal.
As shown in post#3:
GUID_partition_scheme *121.3 GB disk0 and GUID_partition_scheme *1.0 TB disk1 are the Fusion drive components.
Now I will have to look up the right terminal command for erase, probably eraseDisk disk0 etc.
Not sure yet about that.
Edited!
 
Last edited:

davidlv

macrumors 65816
Original poster
Apr 5, 2009
1,260
22
Kyoto, Japan
Try this in Terminal from Internet recovery and tell me what you get.

Code:
diskutil cs delete "Mac HD"
Thanks for the reply!
I got this response; "Mac HD does not appear to be a valid CoreStorage volume or name."
On an Apple Discussion board, I saw this:
"If you're installed Mojave (10.14.2 or later), your Fusion drive has been converted to APFS, hence, no CoreStorage. Which is why you're receiving that return message from Terminal." (I.e., that may mean there is nothing "wrong" with this Fusion drive, so I may have to think about redoing the disk.)
"Post what you get from 'diskutil apfs list'. What you can do is just find the bsd names, likely disk0 and disk1, and unmount them with 'diskutil unmountdisk force disk0' and the same thing for disk1, then erase them individually in terminal."
I also saw some samples:
Samples; from apostle's post about BootCamp
diskutil eraseVolume jhfs+ BC1 disk0s3 ("BC1" is the name of the partition shown by diskutil list, and jhfs+ is the format of the disk after executing the command)
diskutil mergePartitions jhfs+ BCMP disk0s3 disk0s4 (I don't think I would need the "mergePartitions" command)
Still have not decided to erase the Fusion drive. While it is slower than what I am used to (using an SATA Crucial MX500 512GB SSD ) it isnT really "slow".
insert "confusion" or undecisive" emoticons here.
 

Weaselboy

Moderator
Staff member
Jan 23, 2005
29,811
9,446
California
Still have not decided to erase the Fusion drive. While it is slower than what I am used to (using an SATA Crucial MX500 512GB SSD ) it isnT really "slow".
What are you trying to accomplish? Is the Fusion drive working properly, but you just want to try with no Fusion and separate disks?
 

TwoH

macrumors regular
May 19, 2019
148
44
You should simply be able to remove it being APFS by typing this in terminal:
diskutil ap list
Copy physical store ID
diskutil ap deleteContainer **Paste Code Here**

Edit: This will of course delete all data on the drive(s)
 

davidlv

macrumors 65816
Original poster
Apr 5, 2009
1,260
22
Kyoto, Japan
You should simply be able to remove it being APFS by typing this in terminal:
diskutil ap list
Copy physical store ID
diskutil ap deleteContainer **Paste Code Here**

Edit: This will of course delete all data on the drive(s)
Our posts are crossing in the ethernet and I can't keep up with your fast typing!
At firsst I was disappointed in the responsiveness - lack of speed - as I was used to the Crucial MX500, which is snappy
Now I am wonderin' if the low capacity of the installed 121GB SSD will be a problem.
So I may just stop this effort,
Still it is good to know how to do it.

Ran that command:
davidv$ diskutil ap list
APFS Container (1 found)
|
+-- Container disk2 899839C9-26A6-4820-86C3-C4DA83AF11A3
====================================================
APFS Container Reference: disk2 (Fusion)
Size (Capacity Ceiling): 1121118199808 B (1.1 TB)
Capacity In Use By Volumes: 90618408960 B (90.6 GB) (8.1% used)
Capacity Not Allocated: 1030499790848 B (1.0 TB) (91.9% free)
|
+-< Physical Store disk0s2 1FE5F8BE-9361-4145-AA17-BDC07F755B40
| -----------------------------------------------------------
| APFS Physical Store Disk: disk0s2 (Main)
| Size: 121123069952 B (121.1 GB)
|
+-< Physical Store disk1s2 E05E866A-3668-4812-958F-1BC5E7E23DF5
| -----------------------------------------------------------
| APFS Physical Store Disk: disk1s2 (Secondary, Designated Aux Use)
| Size: 999995129856 B (1000.0 GB)
|
+-> Volume disk2s1 27F9E1CE-DEC0-4976-BB74-149635DFAA9D
| ---------------------------------------------------
| APFS Volume Disk (Role): disk2s1 (No specific role)
| Name: Mac HD (Case-insensitive)
| Mount Point: /
| Capacity Consumed: 81255976960 B (81.3 GB)
| FileVault: No
|
+-> Volume disk2s2 F393657A-AD03-42F5-8A67-A5F751224110
| ---------------------------------------------------
| APFS Volume Disk (Role): disk2s2 (Preboot)
| Name: Preboot (Case-insensitive)
| Mount Point: Not Mounted
| Capacity Consumed: 23359488 B (23.4 MB)
| FileVault: No
|
+-> Volume disk2s3 7CF4FDA0-3646-4F08-B218-0CA5A3DD8ED5
| ---------------------------------------------------
| APFS Volume Disk (Role): disk2s3 (Recovery)
| Name: Recovery (Case-insensitive)
| Mount Point: Not Mounted
| Capacity Consumed: 516632576 B (516.6 MB)
| FileVault: No
|
+-> Volume disk2s4 79AE86D2-2576-45B9-ADFC-68BE4BFF9B34
---------------------------------------------------
APFS Volume Disk (Role): disk2s4 (VM)
Name: VM (Case-insensitive)
Mount Point: /private/var/vm
Capacity Consumed: 20480 B (20.5 KB)
FileVault: No

So, Does that **Paste Code Here** mean
diskutil ap deleteContainer 899839C9-26A6-4820-86C3-C4DA83AF11A3
diskutil ap deleteContainer disk2 ?
As you can see abovel there is also
Physical Store disk0s2 1FE5F8BE-9361-4145-AA17-BDC07F755B40
 
Last edited:

TwoH

macrumors regular
May 19, 2019
148
44
So, Does that **Paste Code Here** mean
diskutil ap deleteContainer disk2 899839C9-26A6-4820-86C3-C4DA83AF11A3
diskutil ap deleteContainer disk2 ?
As you can see abovel there is also
Physical Store disk0s2 1FE5F8BE-9361-4145-AA17-BDC07F755B40
Yes, if I remember correctly it should be 899839C9-26A6-4820-86C3-C4DA83AF11A3
 

davidlv

macrumors 65816
Original poster
Apr 5, 2009
1,260
22
Kyoto, Japan
Yes, if I remember correctly it should be 899839C9-26A6-4820-86C3-C4DA83AF11A3
Thanks for the reply.
I assume some terminal commands will be necessary to set up the 2 separate disks, 1 SSD and 1 HD and name them. Using the rather lame Disk Utility may just result in a new Fusion drive (judging from what I have seen on the net).
 

TwoH

macrumors regular
May 19, 2019
148
44
Thanks for the reply.
I assume some terminal commands will be necessary to set up the 2 separate disks, 1 SSD and 1 HD and name them. Using the rather lame Disk Utility may just result in a new Fusion drive (judging from what I have seen on the net).
No, after using that command in terminal, it should break the fusioned drives, and you should be able to simply erase both the SSD and HDD to create partitions for each one separately
 

davidlv

macrumors 65816
Original poster
Apr 5, 2009
1,260
22
Kyoto, Japan
No, after using that command in terminal, it should break the fusioned drives, and you should be able to simply erase both the SSD and HDD to create partitions for each one separately
Thanks to you and Weaselboy!
I am too tired to do this today, back again tomorrow, when I will do it booted up from the internet recovery partition. Then I will reboot from my backup USB drive, and erase/format/partition both drives using Disk Utility and then restore my data.
Thanks again!
 

Fishrrman

macrumors P6
Feb 20, 2009
18,271
6,132
How many drive icons appear on the desktop?
It looks like the internal SSD and HDD are "split apart" already.
 

davidlv

macrumors 65816
Original poster
Apr 5, 2009
1,260
22
Kyoto, Japan
How many drive icons appear on the desktop?
It looks like the internal SSD and HDD are "split apart" already.
Yep, it just works!

Just to set the record straight for all who may have to do this in the future...
1st run "diskutil ap list" from iTerm or terminal to find the physical store ID
Copy the physical store ID
In my case, "diskutil ap list" produced "Container disk2 899839C9-26A6-4820-86C3-C4DA83AF11A3"
and several other entries for other disks.
The last part of that result, after the "disk2" is the physical store ID
use this command
diskutil ap deleteContainer
**Paste physical store ID Here**
!! This will of course delete all data on the Fusion drives. !!

I ran the command above to split the Fusion drive while booted up from a USB SSD formatted as an APFS disk running Mojave 10.14.6.
After an entertaining 30 seconds watching the screen count down to 100%, it settled down and I had 2 HFS+ disks on the desktop. I renamed them, restored my data, and ran Disk Warrior on them.
Now I have an external Mojave SSD I can boot from and use to get any system Updates (HFS+ disks and Mojave don't recognize Apples updates) and 2 HFS+ disks for everyday use. Having Carbon Copy Cloner makes this easy to manage. (and yes Mojave runs fine on HFS+)

Thanks again to Weaselboy and TwoH who made this possible.
 
  • Like
Reactions: Weaselboy

Fishrrman

macrumors P6
Feb 20, 2009
18,271
6,132
I suggest that you put a copy of the OS onto the internal 128gb SSD, along with your apps and basic account.

Why?
To have an always-accessible, immediately bootable copy of the OS if your external SSD won't boot for some reason.

You always always ALWAYS want to keep a fully-bootable-to-the-finder SECOND COPY of the OS within "quick reach".

Also...
Run a speed test on the external SSD and the internal SSD.
What read speeds do you get?
Post them here.
 

davidlv

macrumors 65816
Original poster
Apr 5, 2009
1,260
22
Kyoto, Japan
I suggest that you put a copy of the OS onto the internal 128gb SSD, along with your apps and basic account.
Why?
To have an always-accessible, immediately bootable copy of the OS if your external SSD won't boot for some reason.
You always always ALWAYS want to keep a fully-bootable-to-the-finder SECOND COPY of the OS within "quick reach".
Also...
Run a speed test on the external SSD and the internal SSD.
What read speeds do you get?
Post them here.
Of course, I only booted from the external USB 2 (not 3!) disk to avoid using the recovery partition and switching back and forth, my main OS - boot disk - is the 121GB Apple SSD with clones (CCC) on the 1TB Seagate HD and the external 256GB Plextor SSD in a USB case.
The 6-year-old Apple SSD gets reads and writes speeds of 408.7 and 289.2 respectively, while listening to Mandolin Orange and writing this. The USB would be horrendous, so I haven't bothered with that.
When my next ship comes in, and the profit margin is high enough, I will buy a thunderbolt external SSD and connect it up with an Apple thunderbolt 3 to thunderbolt 2 adapter, to get a decent speed increase and have Trim enabled (as it is on the internal SSD).
Why did you assume I was only using the external USB drive? Tired, lack of sleep or otherwise? The tone of your last post was rather overbearing, so I might just ask that you please don't continue in that vein.
 

Fishrrman

macrumors P6
Feb 20, 2009
18,271
6,132
Look at at the avatar, and you will understand "why I post as I do". That will not change.

USB3 and a SATA SSD will yield read speeds of 420-430MBps.
SSD using the internal SATA connection (where the internal HDD was) might give you 500MBps, maybe a little more.
Thunderbolt might be faster, of course, but perhaps not that much faster, and more expensive.

"Of course, I only booted from the external USB 2 (not 3!) disk to avoid using the recovery partition and switching back and forth"

Why would one need to use the recovery partition to switch back and forth between bootable volumes?
I don't get it. Please explain.
I almost never boot to the recovery partition for any reason.
For years I REMOVED the recovery partition entirely and lived without it.
That's no longer possible with the latest versions of the OS for a couple of reasons:
a. Can't disable SIP without booting to recovery (SIP is TURNED OFF on all my Macs)
b. Can't disable t2 protection without booting to recovery (t2 is DISABLED on my 2018 Mini). ;)
 
Last edited:

mikehalloran

macrumors 68000
Oct 14, 2018
1,646
415
The Sillie Con Valley
A 2012 iMac has two SATA III busses but one is a blade. An external SSD over USB 3 will be about the same speed, if a little slower, not noticeably. Thunderbolt will be no faster than internal and barely faster than USB 3 or not at all. SATA III is your bottleneck.

USB 2 is significantly slower.

With APFS, you will not have access to the Recovery partition if you have more than one Mac OS active on the system. Period. That makes this a bad idea unless it is the only OS installed:

I suggest that you put a copy of the OS onto the internal 128gb SSD, along with your apps and basic account
Likewise, if there's an OS on either internal drive, the Recovery Partition will not be accessible from the external.

Reading this thread, it looks to me that the solution is to open up that 2012, throw the blade away and install a single SSD that's large enough for your needs. 1TB is $107 and 2TB is $200 on Amazon.
MX500 on Amazon

Crucial's turnaround time on warranty exchanges is pretty fast from their Meridian, Idaho service center.

Get a decent tool to test the health of your drives. I use TechTool Pro but there are others, some are free, I think.

The chances that the blade is still good after 8 years are nearly nonexistent.

If you absolutely, positively must have two internals inside a 2012 iMac, get the special harness that adapts a standard SATA III SSD to that socket. However, with 2.5" SSDs available up to 4TB, do you really need two of them installed?
4T WD Blue 3D

It's quite ok to have an OS installed on an external as long as you have a reason to do so — just know that the Repair Partition is unavailable to you if an OS is installed on either or both internals. If you normally boot from the internal and need the Repair Partition for, say APFS Snapshots, you must disconnect the external first.

The only advantage to having an external over Thunderbolt is that you can enable TRIM by typing the following into Terminal

sudo trimforce enable

entering your Admin password, answering Yes to Apples's attempts to discouraging you.

I move files onto and off of my external SSDs all the time while testing—and I do a lot of that—so enabling TRIM speeds the drive recovery time quite a bit. A 2TB SATA III external is completely refreshed in about 24 hours with it; far longer without — this isn't an issue for most users.

This is the TB dock I use. I'll be the first to admit it's a useless expense for most iMac owners — USB 3 is fine. Really. But, if you have needs like mine...
OWC 2x SATA III TB Dock
 
Last edited:

davidlv

macrumors 65816
Original poster
Apr 5, 2009
1,260
22
Kyoto, Japan
A 2012 iMac has two SATA III busses but one is a blade. An external SSD over USB 3 will be about the same speed, if a little slower, not noticeably. Thunderbolt will be no faster than internal and barely faster than USB 3 or not at all. SATA III is your bottleneck.

The chances that the blade is still good after 8 years are nearly nonexistent.

This is the TB dock I use. I'll be the first to admit it's a useless expense for most iMac owners — USB 3 is fine. Really. But, if you have needs like mine...
OWC 2x SATA III TB Dock
Thanks for the reply. The SSD Samsung blade is working fine, if a little slower than I expected. It is formatted as HFS+ and has a recovery partition (Created by CCC when I loaded my data?).
The Seagate 1TB HD is also running fine. And it also has a recovery partition.

After I pruned down my iTunes library and my Movie collection, I now have almost 60GB free on the 121GB blade. In normal use, the stress factor on my machines is very low, and I barely even stress the total of 8GB of RAM on this iMac. I do plan to add 2 8GB chips in the near future.
Splitting the Fusion drive has not significantly increased the responsiveness or speed of the system (no recognizable speed increase), but it does give me another disk to use for a CCC clone.

I have an external SSD drive formatted as APFS so I can get system updates.
 

mikehalloran

macrumors 68000
Oct 14, 2018
1,646
415
The Sillie Con Valley
Thanks for the reply. The SSD Samsung blade is working fine, if a little slower than I expected. It is formatted as HFS+ and has a recovery partition (Created by CCC when I loaded my data?).
The Seagate 1TB HD is also running fine. And it also has a recovery partition.
You tested this — how?

If you didn't test with a good tool that displays all of the parameters, then you don't know if what you posted is true. I use TechTool Pro but I understand that there are some freeware utiities that are pretty good.

Apple's Disk utility is not that tool. I have hundreds of screen shots of failing HDDs and dozens of similar SSDs that Disk Utility shows as Passed.

This shot is a little extreme but not atypical. It's a Seagate HDD from a 2012 Time Capsule. The screen shot was taken in 2015.

full.jpg
 

davidlv

macrumors 65816
Original poster
Apr 5, 2009
1,260
22
Kyoto, Japan
You tested this — how?

If you didn't test with a good tool that displays all of the parameters, then you don't know if what you posted is true. I use TechTool Pro but I understand that there are some freeware utiities that are pretty good.

Apple's Disk utility is not that tool. I have hundreds of screen shots of failing HDDs and dozens of similar SSDs that Disk Utility shows as Passed.

This shot is a little extreme but not atypical. It's a Seagate HDD from a 2012 Time Capsule. The screen shot was taken in 2015.

View attachment 890200
Can you suggest a free utility to do that testing?
I have run Disk Warrior on both of the split Fusion component drives but of course it doesn't show the details like your screen shot, was that was from TechTool Pro?
Considering the age of these drives, it is indeed very possible that they are close to the end of their natural life spans.
I ran the trial version of DriveDX on both drives; no issues found, see the screen shots: I am not familiar with this software, so I don't know how reliable that test suite is.
 

Attachments

Last edited:

mikehalloran

macrumors 68000
Oct 14, 2018
1,646
415
The Sillie Con Valley
Yea, Disk Warrior only rebuilds directories — something that the Mac OS does quite well on its own. Its only other use is as a diagnostic tool — if it's popping a ton of errors, the drive is ready to fail. I used for years but it never fixes anything except directories purposely corrupted by magazine reviewers. Totally useless nowadays other than to separate you from your money. Yes, it lets you delete corrupt preference files that can't harm your Mac (again, the OS generates new ones). Even if it worked for the task they advertise, it's the wrong tool here.

Many use DriveDX. There's a free eval period — $19.99 to buy.
DriveDX

I also use Smart Scope from Micromat — it goes even deeper than TechTool Pro. TTP shows this drive as clean but you can see error data on my Samsung 850 EVO (I don't know if I can send this in for warranty but I will send them this screen shot). $49.95 or $29.95 for TTP customers.

Screen Shot 2020-01-24 at 2.33.40 PM.png


BTW, CRC errors can be the drive, cable or housing. I'll swap it with my other SSD in the same dock — if I get the same errors, it's the SSD. That's why it's important to know what the tests are telling you — fields in red aren't always enough.
- - Post merged: - -

One more thing. You cannot access SMART data over USB, only SATA, eSATA, PCI and Thunderbolt.
 
Last edited:

smbu2000

macrumors 6502
Oct 19, 2014
298
137
Is the fusion drive that slow? Is it faster to run mainly from the internal 128GB blade ssd?
I have a late 2012 27” iMac coming that has a 1TB fusion drive setup. The os is only installed on the 128GB ssd and is not setup as a fusion drive. I was curious about leaving it as is or recreating the fusion drive.
i also have an extra 500GB ssd that I could connect with a USB3/Thunderbolt case that I have.