We help IT Professionals succeed at work.
Get Started

iMac Disk Utility First Aid Failed

Last Modified: 2016-01-10
I have an iMac 27" Retina 5K (Late 2015) El Capitan (10.11.2) and Windows 10 via Bootcamp.   This morning after I had finished some work on the Windows side of the machine, I tried to boot up into El Capitan but it silently failed and the machine turned itself off at about the 2 minute point.  Tried again and same problem.  So I checked if I could get back into Windows and ran Windows 10 with no problem.  Next I booted into the Mac recovery partition to run Disk Utility and it revealed an enormous number of errors on the Macintosh partition such as:

- Previous ID in a hard link chain is incorrect (ID = -1130612101)
(it should be 3164355194 instead of 0)
Many of the above errors appeared with different numbers
- Volume bitmap meds minor repair for orphaned blocks
- Invalid volume free block count
- Volume header needs minor repair
- Missing thread record (id = -1130634630)
Many of the above errors appeared with different numbers

Finally the process 'finished' with "First Aid process has failed.  If possible back up the data on this volume"

Next I booted into a USB installed version of El Capitan and while that was successful, it gave a warning when it mounted the volume that I was having the problem with: "OS X can't repair the disk 'Macintosh HD'" but I was able to copy files from that volume and even run applications that were stored on it.  Tried running Disk Utility and First Aid again but failed as above.

So here are the questions.

1.  Should I assume there's nothing else that can be done other than erasing that partition and reinstalling El Capitan?

2.  Will erasing the partition and reinstalling El Capitan affect my Bootcamp partition or ability to use Win 10?

3.  I have a Time Machine backup; will restoring it re-introduce the same problem?

4.  I've never had such a massive and unrecoverable failure on a Mac drive and I had used it the night before with no problem.  Should I assume the disk itself is faulty and have it replaced?  I ran an Apple Hardware Test and no problems were indicated.
Watch Question
This problem has been solved!
Unlock 2 Answers and 7 Comments.
See Answers
Why Experts Exchange?

Experts Exchange always has the answer, or at the least points me in the correct direction! It is like having another employee that is extremely experienced.

Jim Murphy
Programmer at Smart IT Solutions

When asked, what has been your best career decision?

Deciding to stick with EE.

Mohamed Asif
Technical Department Head

Being involved with EE helped me to grow personally and professionally.

Carl Webster
CTP, Sr Infrastructure Consultant
Ask ANY Question

Connect with Certified Experts to gain insight and support on specific technology challenges including:

  • Troubleshooting
  • Research
  • Professional Opinions
Did You Know?

We've partnered with two important charities to provide clean water and computer science education to those who need it most. READ MORE