Partition on External HDD won't mount

Hi, there’s one partition on my seagate external usb hard drive that won’t mount. It may have happened after my MacBook pro battery died. The HDD is formatted as Mac OS Extended (Journaled) with 5 partitions.

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I ran Disk Utility’s first Aid on the drive and each partition. First Aid fails on the partition that won’t mount.

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  1. How can I recover data on the partition? I’m ok if I can’t recover.
  2. Should I reformat the partition and continue to use it?
  3. What diagnostic tests or tools can I run on the external hard drive? Should I be worried the HDD is about to fail?

Tech Details

The MiniTool free Mac data recovery software is supposed to deal with partitions that don’t mount.

If this app doesn’t help, you’re looking at a 3rd party tool like Alsoft’s Disk Warrior or Prosoft’s Data Rescue to try to pull data from the partition, software which runs $70-$100. Hopefully you have a recent backup…

Didn’t work for me. I’m ok with losing the data and starting that partition over.

Do you think if I reformat the partition, that I’ll be ok? Is there a diagnostic tool to check the hard drive?

  1. Disk Utility -

  2. If you are a Setapp subscriber:

  3. Tools like Drive Genius, Disk Warrior (as mentioned by @bowline).

Be careful: do not trust the HDD’s reliability too much. When a HDD starts failing, it is never a good sign. Usually, there is no happy ending.

That’s a good point. If you have a partition that’s failed you might want to consider it a sign to migrate to a new drive. If I had a failure like this one I’d probably replace it, under warranty or not.

Modern drives with high data density and spin rates have definite lifespans. A while back Backblaze looked at the drives it was using and found a jump in failure rates of between 9% and 17% between years three and four of their drives running 24/7, with an average annual failure rate of almost 12% by Year 4.

Because drives inevitably fail I replace working drives every five years.

Thanks for the useful information. It’s my project for the weekend. The hard drive should still be under warranty so I’ll have to run through Seagate’s warranty protocol.