Been having issues with Time Machine and backup so I ran disk utility on all my drives: iMac drive, iomega external HD and Time Capsule. When I run on Time Capsule I am getting a failure and this message:

Updating boot support partitions for the volume as required.
Unable to mount volume for repair.
Operation failed…

Time Machine says "last backup Nov 25, 2015." Can't figure out what is going on. Does anyone have any suggestions?

  • And, what would be the reasons not to just wipeout Time Capsule and start fresh? I am pretty sure I have everything backed up elsewhere. Time Capsule is 1TB and appears to be close to full...even though my Mac HD only has about 400GB used out of 1TB.
    – Sizzle
    Dec 21, 2015 at 18:08
  • If you are confident you have appropriate backups other then Time Machine and you want to start fresh, then I see no reason why you can't wipe the drive used for TM backups and start anew. It is after all your decision to make. Dec 21, 2015 at 18:11
  • Thanks...I am throwing it out there because I can often times overlook something that someone else might see. Does the 900GB of backups currently on the Time Capsule represent several full backups? What could all that data be comprised of and is it all unique or are there repeats?
    – Sizzle
    Dec 21, 2015 at 18:18
  • 1
    Suggest you do some reading... Use Time Machine to back up or restore your Mac and How Time Machine Works its Magic. You can look at the contents of the Time Machine Backups from a different perspective then Time Machine itself using apps like BackupLoupe and also TimeTracker under "Odds and Ends" on the page this last link brinks up. Dec 21, 2015 at 18:26
  • Thanks for the answer...but I am trying to get an understanding of why Disk Utility is giving me "Operation Failed" message and why it won't back up...after having been fine and backing up for about 5 years. Any idea?
    – Sizzle
    Dec 21, 2015 at 20:21

3 Answers 3


TimeMachine is rock solid. I have used it extensively and exclusively since it came out at on many different machines and have never lost any data. Like any backup system, it is only as reliable as the person using it. You need to have multiple disks rotated at regular intervals. Time Capsule is just one Time Machine disk, so don't confuse the two. You need additional Time Machine backups on other disks. Unfortunately all disks fail eventually. If it says that the last back was a certain date then that is what you have.


Disk Utility can only check backup disks in recovery mode. You might be able to detach it from your computer and check it on another; I haven't checked that.

For more information, see this excellent article by Howard Oakley.


You do not want to fix it but understand what is going on? There are several components to this answer.

  1. Time Machine is unreliable software. It has failed so often for so many people. Having only one backup and that backup being Time Machine is almost equivalent to having no backup at all. Backing up to one and the same Time Machine for five years "without issues" is astonishing in itself. Time Machine reliability seems to get worse over time: one example to move away from pure opinion. Lesson: do not rely solely on Time Machine.

  2. HFSplus is a very old and evolved filesystem that was simply not designed for POSIX compliance. Hardlinks being a requirement for that and Time Machine. Apple's implementation for that is highly non standard and added on as an afterthought. Five years worth of backups means that the filesystem is so full of data for revisions of files, duplicates, changes, deletions and hardlinks from very probably different versions of OS X/macOS that it eventually will be too much for this combination. Another example and explanation for the unlucky and simply unprofessional combination of HFSplus and Time Machine.

  3. Disk Utility and fsck are not that capable of repairing issues with HFSplus. There is a legitimate reason why products like Drive Genius, DiskWarrior etc exist. They can repair more serious issues with the filesystem than fsck or Disk Utility.

  4. Apart from those systematic reasons there is of course the most simple possibility: unfortunate things do happen. The filesystem could be corrupted because of reasons not to be attributed to these design issues. Bit flips, bit rot, hardware problems like bad sectors etc. An age of five years (at least that) isn't exactly young for a drive.

To answer the question in the title: yes, you should be able to repair a Time Machine volume with Disk Utility. Problem being that sometimes you simply can not. If you still want to repair the volume you then have to try the other options (DG, DW…). If you want that data back, try to restore it to a big enough volume. Revisions might get lost that way. Or try to copy that volume via rsync or dd to another volume, then copy/restore that back to a freshly formatted Time Capsule.

  • 1
    The first link is a very bad example to support your thesis/assumption. It's a good example how not to work with Time Machine (i.e. restoring something to a source drive with two volumes each containing a clone (clone ≠ backup) of the source drive still attached).
    – klanomath
    Aug 26, 2017 at 10:55
  • Time Machine doesn't use HFS+ on new setups
    – Ezekiel
    Aug 23, 2022 at 2:53
  • @Ezekiel "on new setups"… is 'a thing' a post from 2017 cannot account for… Aug 23, 2022 at 8:07
  • Yes I realize that, my apologies - always throws me off how Stack Overflow surfaces old content
    – Ezekiel
    Aug 23, 2022 at 17:28

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