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I have a Late 2015 iMac 27", running Mojave. I routinely run disk utility. Today, disk utility failed on the internal Fusion drive, and on two external hard drive, one being my Time Machine. I am wondering (hoping) that the issue is the disk utility program. I am looking for advice on what I should do to narrow done a path to a solution. The computer still functions (using it now) and Time Machine just backed up w/o issues.
iMac 27″, macOS 10.14
I would believe what Disk Utility says. However running Disk Utility in "live mode" to check your internal drive may be not as reliable as running it from another boot volume. Boot into Recovery (COMMAND-R while booting) and run Disk Utility First Aid from there on your internal drive. If it fails, you need to reliably back up and replace the drive.
If Disk Utility also shows failure on external drives they may be failing also. For instance, if your electrical power has surges or brownouts that can damage computers and drives and result in failing Disk Utility.
DriveDX provides a more detailed and comprehensive assessment of the state of your disk. I have had disks that passed as "ok" in Disk Utility but showed serious problems in DriveDX.
I would believe what Disk Utility says. However running Disk Utility in "live mode" to check your internal drive may be not as reliable as running it from another boot volume. Boot into Recovery (COMMAND-R while booting) and run Disk Utility First Aid from there on your internal drive. If it fails, you need to reliably back up and replace the drive.
If Disk Utility also shows failure on external drives they may be failing also. For instance, if your electrical power has surges or brownouts that can damage computers and drives and result in failing Disk Utility.
DriveDX provides a more detailed and comprehensive assessment of the state of your disk. I have had disks that passed as "ok" in Disk Utility but showed serious problems in DriveDX.
What was the error message from Disk Utility? A disk can continue to function even if the disk is starting to degrade or fail. Backing up should be done extra diligently now if you are getting Disk Utility failures.
kennethfromdavis wrote:
The Fusion Drive "passed" First Aid and the closing messages was: "Performing deferred repairs: Warning: found physical extent corruption but repairs disabled." "The volume . . . appears to be ok." "File system check exit code is 0."
Unfortunately Apple now allows Disk Utility to report everything is "Ok" even when there are unfixed errors. I've personally seen this with some of our organization's Macs where the errors caused major problems including mounting the drive and creating Kernel Panics. When you got this error were you booted into Recovery Mode or Internet Recovery Mode (Command + Option + R)? I wasn't sure since this was separated from the mention of Recovery Mode. I would be concerned about this error if it cannot be repaired.
The log for Snapshot 1 had 71 lines similar to this: "error: Cross Check: Mismatch between external entry reference count (1) and calculated fsroot entry reference count (0) for extent (0x4000014f853b+2). Snapshot 2 had 71 lines corresponding to log entry for Snapshot 1 - "error: Cross Check: External Ref physical extent (0x4000014f853b+2) has Kind APFS_KIND_UPDATE but was not referenced previously"
In theory the APFS snapshot errors should not affect normal system operation and these errors should be gone once the APFS snapshot is deleted (this usually happens automatically within a week or after the backup has completely transferred to the external drive).
From I read on the DriveDx page, it says it works on the Fusion drive. However, the trial version appears not to run on Mojave.
It should run fine on Mojave unless you have some other third party software interfering (anti-virus, cleaning apps, or security software) or unless the file system errors are interfering. Try booting into Safe Mode to see if you have any better luck running DriveDx.
DriveDx only concerns itself with physical drives and a Fusion Drive will appear as two separate physical drive. We definitely need the health report for the hard drive, but if you want to post the report for the SSD as well that will be fine. You will need to click on the physical drive and select "Save Report". You need to do this for each individual drive you want checked. You may be able to check the external drive(s) as well, although it will require a special USB driver to be installed (you will be prompted by DriveDx), but even then some USB drives don't allow the necessary communication to occur.
Copy that on the snapshot errors.
Ran the trial version of DriveDx. The external I use for Time Machine did not fair well, but I was able to get a fresh backup with a new unused external drive.
Fusion SSD:
Fusion HDD:
Thank you for your reply.
”First aid process has failed. If possible back the data on this volume.” I have read that a disk may still function while it is going bad. I have had no indications that either of the three disks was in trouble. I am also confused that if the disks had problems, why did First Aid find them all during the same session of running First Aid on all my drives. Thus, my. Question if DU is the problem.
Disk Utility only runs First Aid on the main directory files it does not run diagnostics on the Disk,
if you really want to know the health of your disks then download and run this,
https://binaryfruit.com/drivedx there is a free trial period.
Why do you run Disk Utility frequently, what are you hoping to achieve.
Thank you, steve626.
Frankly, I am not knowledgeable, so I appreciate your assistance. Especially, telling me the possible effects of power surges on leading to failing Disk Utility. I've trusted DU this far into my Mac ownership, I thank you for mentioning "DriveDX". I will look into it.
I forgot to mention I boot into Recovery Mode to run DU/First Aid on the Fusion drive. I re-ran it last night and my Time Machine external drive "passed" with no mention of what it could not accomplish, a 180 degree result from the previous ruining. The other, less important external drive still flunked the test.
The Fusion Drive "passed" First Aid and the closing messages was: "Performing deferred repairs: Warning: found physical extent corruption but repairs disabled." "The volume . . . appears to be ok." "File system check exit code is 0."
The log for Snapshot 1 had 71 lines similar to this: "error: Cross Check: Mismatch between external entry reference count (1) and calculated fsroot entry reference count (0) for extent (0x4000014f853b+2). Snapshot 2 had 71 lines corresponding to log entry for Snapshot 1 - "error: Cross Check: External Ref physical extent (0x4000014f853b+2) has Kind APFS_KIND_UPDATE but was not referenced previously"
Thank you for your reply, Eau Rouge.
Another Community Member also recommended DriveDx, so thank you. I will look into DriveDX. It appears, I do not have handle on the purpose of Disk Utility.
Why do I run Disk Utility frequently? Good question. Probably because of my experiences during my PC days of "defragging" the hard drive. With adding/deleting documents, deleting obsolete programs/applications and the adding/deleting during photography post-processing, I feel there are continuous fragmentation of the disk. I have no scientific rationale.
Remember, Disk Utility just reveals the condition of your drives.
I am very uneasy about those errors from the Fusion drive. Let’s see what others say about that.
There is also something not right about your externals.
if this were me, I’d get a good power strip to protect against power fluctuations, and back up everything. I think I would reformat and restore the Fusion drive and the external that failed. Since I use SSDs this gets very expensive. Maybe others will chime in and say the Fusion drive errors are not a concern ...
Also, I’m not sure if DriveDx runs on Fusion drives.
Of course DriveDX runs on macOS Mojave we would not have recommended it if it did not.
Disk Utility does not defrag your mac, so running First Aid is achieving nothing.
The mac will defrag small files on a power up, you can boot into Safe Mode occasionally
if you want to run repairs to your internal disk and empty caches.
Macs do not need any apps that claim to clean, optimise or make your mac
run faster than a speeding bullet.
The mac is best left alone it manages itself quite well without interference, sometimes the worst thing
for macs are the owners themselves.
steve626 wrote:
The snapshots errors, while not directly affecting operation, seemed to me to be indicative of drive corruption and hence could be indicative of a problem with the volume or drive.
I agree too. Definitely need the DriveDx report(s) to try to rule out a hardware failure.
Thank you, steve626. Looking forward to what others comment.
From I read on the DriveDx page, it says it works on the Fusion drive. However, the trial version appears not to run on Mojave.
The snapshots errors, while not directly affecting operation, seemed to me to be indicative of drive corruption and hence could be indicative of a problem with the volume or drive.
Post the entire DriveDx report for each drive. The information contained in the full report for each drive may reveal important information.
Disk Utility Failure
