My Book 3 TB Suddenly Became Read Only

I have been using an external 3 TB My Book for my Time Machine backups for almost a year now.  It still has at least 1TB of space left.  When I connected it to my MacBook Pro yesterday, it is now Read Only. The HD does not mount immediately, but mounts after about 20 minutes the following message:

Mac OS X can’t repair the disk “Time Machine Backups.”

You can still open or copy files on the disk, but you can’t save changes to files on the disk. Back up the disk and reformat it as soon as you can.

All the Time Machine backups are available. I have tried the following:

  • Get Info to reset permissions–I can unlock the padlock but the ‘everyone’ permissions cannot be changed.

  • Disk Utility–Verify and Disk Repair give errors.

- DiskWarrior says there is a hardware error.

  • Resetting the permissions using Terminal.  The commands used: 

  sudo chflags nouchg /Volumes/“Time Machine Backups”

  chmod 775 “/Volumes/Time Machine Backups/”

No joy on any of that.  

Some background that may be useful: We lost power during the recent ice storm in Georgia.  The My Book was connected and plugged in at the time.  So, it was not unmounted properly.  Then I went on travel for two weeks and did not take the My Book with me.  It was when I returned that I discovered the Read Only status.

My system info:

Computer: MacBook Mid-2009 model

Memory: 8GB

OS: OSX 10.8.5

Any thoughts from the community would be helpful.


Seems like the partition is corrupted. I recommend reformatting the drive. Please note this will delete all data stored on it.

Thanks for the recommendation.  I was hoping that I wouldn’t have to reformat the drive, but it does seem to be the only way to start using it for Time Machine backups again.

Do you have an idea what would cause the problem and how I can prevent it in the future?