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My Time Machine drive is getting disk errors. I used Disk Utility and ran "Repair Disk" on my Time Machine partition (NOT the drive) and I got the error "Incorrect number of directory hard links" including hundreds of related errors that look like "Indirect node 41745332 needs link count adjustment". The final line of the verification says "Error: Disk Utility can’t repair this disk. Back up as many of your files as possible, reformat the disk, and restore your backed-up files."

So, if I get a second drive to copy my Time Machine backups to, can I just move the backups to the new drive by performing a simple "copy" operation as outlined here? Or should I use Disk Utility to clone the partition? And if I do one of these steps, would the errors copy over as well or would they be fixed on the new drive?

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4 Answers

It sounds like you might be out of luck if Disk Utility was unable to repair your partition. You are also correct that a clone of your Time Machine partition would copy over the problem to a new drive. It is probable that your best "solution" at this point would be to erase the partition and start Time Machine backups again. If you end up doing this I would also make sure to run "Verify Disk" on your internal HDD (or SSD if that's what you have) to make sure there aren't any errors there, either.

This might be a symptom of a failing drive; however, it is also possible that it might simply be a bunch of directory errors that can be repaired if you boot from a recovery partition, clone, or use another Mac to repair. I have had both dying drives and drives that looked like they were dying, but were actually just errors piled on one another. Before you throw the drive away, try repartitioning. Do systematic checks with Disk Utility and keep an eye on system logs (either in Console.app or /var/logs/system.log). If you continue to see the same problem, then it is indeed time for a new backup drive; however, you might find that a quick erase fixes the issue.

Also, see this article over at Pondini.org. The article essentially corroborates what I've already said, but the rest of the site is an excellent resource for all the headaches that Time Machine can throw your way.

Sorry you have a bunk backup - hope you get it sorted without much extra trouble!

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I would not erase and repartition - the actual hard disk is dying you have to throw it away –  Mark Feb 24 '13 at 23:30
    
True, this could be the case if we know that the HDD is dying and writing spuriously. The other side is that this is just a series of directory errors. Both are equally plausible given the limited information from the OP. To your point, I should have noted this in my original answer, which is now updated. –  soxman Feb 26 '13 at 8:36
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I don't like: "I ended up following the instructions in the article I linked to in my original post to move my Time Machine backups to a new drive".

The instructions on how to copy TM backups is intended for copying known good backups. It sounds like your backup is NOT known good. You now have a valid file and block structure on the new volume, but how do you know that the data (i.e. the content of files) is correct? If the data on the old volume had errors, then you will have copied the errors to the new disk.

If you have any doubts about the old disk (and it sounds like you have), then do a new TM backup to the new drive. Then you can be confident that you have a good backup of your system in case you have a disaster.

In summary: Never use a doubtful disk for backup - it is what you rely on in the event of loss of your main disk. Never copy doubtful data to a new disk and expect it to be correct.

This really is the same as soxman's advice. But I was alarmed that you may now have bad data in TM, but think that it is ok.

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I would get a brand new drive and start backing up to it.

The existing drive might deliver a perfect copy of your backup files, but since Time Machine uses hard links, I'd hate for the one copy of an important backup file to look like it's there and in reality be gone or corrupt.

Your drive has corruption and if it didn't hold potentially the only copy of your backup data, you would just wipe the drive and try again. Many times, these errors are an accounting error and starting fresh lets a physically fine drive work. It's strike one, and if that drive gets more errors, you would send it in for service / warranty exchange or put it on a shelf.

In the case of backups, I am more quick to retire a flakey drive and start anew. With 3 TB USB 3 drives going for about $100 US, it's silly to waste too much time and effort on a flakey drive - especially if your backups are at risk.

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up vote 0 down vote accepted

I ended up following the instructions in the article I linked to in my original post to move my Time Machine backups to a new drive. It took 28 hours to transfer 1.9 TB of backups. I then ran Disk Utility "Verify Disk" on it and it was good. So, the errors did not transfer over.

So now, I can just repartition the old drive to get rid of all the errors, which I will do after a few days of ensuring that this copy of my backups is indeed good.

I later tested the transferred backup by reformatting my iMac and restoring from the TM backup, and it worked fine (I'm on it now).

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