User profile for user: waltzco
waltzco Author
User level: Level 1
0 points

FUSION Drive SMART Status failing but SMART Status on both HDD and SSD are fine.

I have an iMac 2017 (5K Retina, iMac18,3), and I cannot re-install MacOS 10.15.7, saying there are SMART errors on my internal boot drive. I checked the hardware in System Information and I'm a bit confused on the SMART Status reported by the System Report:


======================

NVM Express:
Apple SSD Controller
  APPLE SSD SM0128L
  Capacity:	121.33 GB (121,332,826,112 bytes)
  TRIM Support:	Yes
  Model:	APPLE SSD SM0128L
  Revision:	CXS7CA0Q
  Serial Number:	****
  Link Width:	x4
  Link Speed:	8.0 GT/s
  Detachable Drive:	No
  BSD Name:	disk0
  Partition Map Type:	GPT (GUID Partition Table)
  Removable Media:	No
  S.M.A.R.T. status:	Verified
  Volumes:
EFI:
  Capacity:	314.6 MB (314,572,800 bytes)
  File System:	MS-DOS FAT32
  BSD Name:	disk0s1
  Content:	EFI
  Volume UUID:	E783267B-A4C3-3556-B751-DBED770EB996
disk0s2:
  Capacity:	121.02 GB (121,018,208,256 bytes)
  BSD Name:	disk0s2
  Content:	Apple_APFS

======================
SATA/SATA Express:
Intel 10 Series Chipset:
  Vendor:	Intel
  Product:	10 Series Chipset
  Link Speed:	6 Gigabit
  Negotiated Link Speed:	6 Gigabit
  Physical Interconnect:	SATA
  Description:	AHCI Version 1.31 Supported

APPLE HDD ST2000DM001:
  Capacity:	2 TB (2,000,398,934,016 bytes)
  Model:	APPLE HDD ST2000DM001                   
  Revision:	AQ03    
  Serial Number:	*****
  Native Command Queuing:	Yes
  Queue Depth:	32
  Removable Media:	No
  Detachable Drive:	No
  BSD Name:	disk1
  Rotational Rate:	7200
  Medium Type:	Rotational
  Partition Map Type:	GPT (GUID Partition Table)
  S.M.A.R.T. status:	Verified
  Volumes:
EFI:
  Capacity:	209.7 MB (209,715,200 bytes)
  File System:	MS-DOS FAT32
  BSD Name:	disk1s1
  Content:	EFI
  Volume UUID:	0E239BC6-F960-3107-89CF-1C97F78BB46B
disk1s2:
  Capacity:	2 TB (2,000,189,177,856 bytes)
  BSD Name:	disk1s2
  Content:	Apple_APFS

======================
Storage:
Macintosh HD:
  Free:	914.85 GB (914,851,737,600 bytes)
  Capacity:	2.12 TB (2,121,207,386,112 bytes)
  Mount Point:	/
  File System:	APFS
  Writable:	No
  Ignore Ownership:	No
  BSD Name:	disk2s5
  Volume UUID:	35F549A5-3D2F-4EA8-B1D4-2048CDE44439
  Physical Drive:
  Device Name:	APPLE SSD SM0128L
  Media Name:	AppleAPFSMedia
  Medium Type:	SSD
  Protocol:	PCI-Express
  Internal:	Yes
  Partition Map Type:	Unknown
  S.M.A.R.T. Status:	Failing

Macintosh HD - Data:
  Free:	914.85 GB (914,851,737,600 bytes)
  Capacity:	2.12 TB (2,121,207,386,112 bytes)
  Mount Point:	/System/Volumes/Data
  File System:	APFS
  Writable:	Yes
  Ignore Ownership:	No
  BSD Name:	disk2s1
  Volume UUID:	81422665-2D80-3115-A417-179E36CBA97D
  Physical Drive:
  Device Name:	APPLE SSD SM0128L
  Media Name:	AppleAPFSMedia
  Medium Type:	SSD
  Protocol:	PCI-Express
  Internal:	Yes
  Partition Map Type:	Unknown
  S.M.A.R.T. Status:	Failing

============

APPLE SSD SM0128L on NVM Express: this is the SSD portion of the Fusion Drive

APPLE HDD ST2000DM001 on SATA/SATA Express: this is the HDD portion of the Fusion Drive

Individually, both items above are reporting SMART status OK.


This is now the confusing part:

Macintosh HD and Macintosh HD - Data on Storage:

It's telling me that the physical drive (APPLE SSD SM0128L) has SMART status failing.


Note: When I run the First Aid, Macintosh HD returns no error, but Macintosh HD - Data has the following errors:

error: (oid 0x40000002dc3af) om: btn: invalid o_cksum (0x6c6d783f3cbfbbef)



So which one should is failing so it can be replaced: the HDD (ST2000DM001) or the SSD (SM0128L), or both?


Thanks in advance!

Posted on Dec 27, 2025 1:19 AM

Reply
3 replies
User profile for user: D.I. Johnson
D.I. Johnson
User level: Level 7
33,065 points

Dec 27, 2025 7:14 AM in response to waltzco

Start by making sure you have a backup of any data that is important to you. As you work through this problem there's a good chance that you may need to erase the drive(s).


Then download a copy of Drive Dx from Binary Fruit and run the diagnostics on your drives. That utility is excellent at drilling down into the particulars of your drives and can provide a clearer picture of just what is going on there.

Reply
User profile for user: HWTech
HWTech
User level: Level 9
68,846 points

Dec 27, 2025 11:59 AM in response to waltzco

waltzco wrote:

I have an iMac 2017 (5K Retina, iMac18,3), and I cannot re-install MacOS 10.15.7, saying there are SMART errors on my internal boot drive. I checked the hardware in System Information and I'm a bit confused on the SMART Status reported by the System Report:

============
APPLE SSD SM0128L on NVM Express: this is the SSD portion of the Fusion Drive
APPLE HDD ST2000DM001 on SATA/SATA Express: this is the HDD portion of the Fusion Drive
Individually, both items above are reporting SMART status OK.

This is now the confusing part:
Macintosh HD and Macintosh HD - Data on Storage:
It's telling me that the physical drive (APPLE SSD SM0128L) has SMART status failing.

Unfortunately Apple makes a mess of these things. And Apple tends to deal with volumes rather than physical drives, hence why you only see the failing status on the volumes instead of the physical drives. Apple just has to think different in a bad way.


Note: When I run the First Aid, Macintosh HD returns no error, but Macintosh HD - Data has the following errors:
error: (oid 0x40000002dc3af) om: btn: invalid o_cksum (0x6c6d783f3cbfbbef)

Not surprising since the "Macintosh HD" volume is the read-only signed & sealed system volume. The "Data" volume is the writable volume containing all of the files that can be modified so it will be the most likely place file system errors will accrue.


So which one should is failing so it can be replaced: the HDD (ST2000DM001) or the SSD (SM0128L), or both?

The odds are in favor of the internal Hard Drive portion of the Fusion Drive. You can use DriveDx as suggested by @D.I. Johnson to confirm.


I hope you have a good backup, but if not, then you should focus on that first assuming the Hard Drive failure is not too severe yet.

Reply

FUSION Drive SMART Status failing but SMART Status on both HDD and SSD are fine.

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