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How to Recover Unmountable Hard Drive on Mac OS X?

Wondershare Recoverit Authors

May 28, 2024 • Filed to: Answer Hard Drive Problems • Proven solutions

Q: How many times have you faced the issue of an unmountable hard disk on your Mac?
I connected my external hard disk of 3TB to my MacBook Air, though it couldn't mount. However, it detected the hard drive when I ran Disk Utility. Is there any way to get back or recover the data from this unmounted disk of my Mac?

Usually, Mac hard drives are partitioned into different sections, also known as logical volumes. It allows you to store a wide variety of data on it separately. The benefit of the partition system is that there is no risk of overloading on the startup disk volume. That allows the boot process to complete without any issues.

There are times when the drive doesn't mount, preventing your system from starting. It is a critical situation because your data stores on the hard disk, and it is now not accessible. There is also the risk of the data getting lost.

Part 1: How to Recover Data from an Unmountable Drive on Mac?

It commonly occurs that the external hard disk becomes unmountable and results in data loss. Even the disk utility may not help you repair the unmounted volume. In such a situation, the right step to take is to recover your data from the unmountable drive.

You can recover your files from an unmountable volume on your Mac OS X by downloading and installing the Recoverit Data Recovery tool for Mac. You should then follow these steps to access all the data.

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Step 1: Launching Recoverit

Open Recoverit Mac Data Recovery tool. Select the hard drive volume that has the issue of lost data. Click on 'start.'

launch recoverit

Step 2: Scanning

Recoverit data recovery starts scanning to find the lost data from the drive. Give it some time to complete the scanning process.

scan the drive

Step 3: Check and recover files

Once the scanning ends, it becomes possible to check all the recoverable files. You can preview these files on the volume and recover them to a location of your choice.

preview and recover

Part 2: How to Repair Unmountable Hard Drive on Mac?

When you face the problem of unmountable hard drive volume, the first thought that comes to your mind is to use the Disk Utility to recover it. There is a built-in feature in Disk Utility, known as First Aid. It allows you to check volume errors and make attempts to repair them.

However, using First Aid is not a favorable method. Firstly, it is often seen to fail to repair errors at times. Secondly, it is likely to cause damage to the data, making it impossible to recover it.

Method 1: Repair an Unmountable Mac Hard Drive Using Disk Utility

Disk Utility is capable of repairing specific drive issues. You can use it when your Mac volume gives the unmountable error.

  1. Open Apple Menu.
  2. Click on 'restart.'
  3. Press and hold the buttons Command and R.
  4. Keep pressing until you see the Apple Logo.
  5. Click on Disk Utility.
  6. Click on Continue.
  7. Select the option 'View.'
  8. Choose 'show all devices'.
  9. Select the volume that you want to repair from the sidebar.
  10. Click on 'First Aid.'

click first aid

  1. Disk Utility may inform that the Mac hard drive is likely to fail. Make sure to take data back up and replace with another drive.
  2. If Disk Utility doesn't make that message, take the next step.
  3. Click on 'Run.'
  4. Disk Utility may inform you that the drive is repaired.
  5. If Disk Utility doesn't give this message, you will have to format the unmountable hard disk before restoring it.
  6. If the 'repaired' word comes, you can use the drive without any issues.

Method 2: Repair an Unmountable Mac Hard Drive by Formatting

Once the data has been recovered, it is necessary to reformat the drive that had the unmountable error. It will ensure that it starts working correctly again. The steps involved are as follows:

  1. Go to Utilities and Open Disk Utility.
  2. Click on the icon showing your hard drive volume from the sidebar.
  3. Click on the 'erase' tab and fill the required information.
  4. When the 'erase' button appears, click on it and the formatting will begin.

click first aid

Learn More:
How to Delete Windows Bootcamp Partition from Mac
9 Best Partition Managers for Mac

Part 3: Signs & Potential Reasons for an Unmountable Hard Disk

Every time your Mac system boots up, it is going to run a self-test. It is then that the startup disk is mounted, and the files needed for launching the OS gets loaded. Therefore, the startup disk volume must mount appropriately. Otherwise, it may become difficult to access the required data.

As already mentioned, there are many reasons why such a situation arises. Find out the most common reasons here.

It may happen that some type of unexpected error has occurred in your Mac volume. Such errors can make the volume unmountable, preventing the data from showing up. Here are the causes of unmountable hard disks:

If the Mac hard disk is insurmountable, it significantly increases the risks of notable losses in terms of essential files like photos, emails, and work documents. If it happens, you will want to know the ways to recover your unmountable and inaccessible hard disk on Mac and the files stored on it.

Part 4: Symptoms and Causes of an Unmountable Hard Drive

Symptoms of an Unmountable Hard Drive

Many symptoms may show that your Mac's hard disk is on the verge of crashing. You should know that the disc is going to unmount if you see the following signs:

Possible Causes

The signs of a hard drive dimming out within Disk Utility can vary from one situation to another. So you should know about these different reasons to be able to determine how to repair the external hard disk that fades within Disk Utility.

Virus or Malware Attack

Once the hard drive has a virus infection, it can cause your system files to get corrupted. It can cause the hard disk to become unmountable. The result is a hard drive that is merely unmountable.

Corruption of File System

The volume data becomes inaccessible to the Mac OS X if there is corruption in the local file system structure. Some of the contributing reasons for file system corruption include erroneous formatting, erroneous re-formatting, or incorrect file system conversion.

Corrupt Volume Header

The volume header is necessary for providing the required data to the operating system. It makes use of header information for mounting a specific volume. Volume can become unmountable when there is a corruption of volume header.

A Hard Drive with Bad Sectors

Bad sectors may also cause an unmounted Mac hard disk. It usually occurs when some type of physical damage happens to the drive. These bad sectors gradually deteriorate and can become entirely useless for storing data. The data stored in this sector will also become difficult to access. Hard drives are known to be highly sensitive to fluctuations in power. So, this can also cause the development of bad sectors. When there are bad sectors, Mac OS X can fail to access the data either partially or entirely.

Operating System Malfunction

The hard drive volume may have become unmountable because the OS crashed.

Sudden Mac Reboot

Your Mac hard drive may also be damaged by the unexpected shutdown of the Mac system. It may happen by an immediate reboot or power failure.

Failure of Disk Utility

You can use the Disk Utility tool for a wide range of tasks, including resizing, file system conversion, and re-partitioning. If an error occurs during these functions, it can render the Mac hard disk volume unmountable.


So, your hard drive volume can become unmountable because of reasons like Disk Utility failure, File System corruption, and Mac OS issues. If you have this issue, it is essential to recover data from such a drive at the earliest.

Using Recoverit Data Recovery software allows you to recover the data from your unmountable Mac hard disk in just minutes. It is a sophisticated hard disk file recovery tool for Mac. It has advanced data recovery features, yet it is easy to use for getting your data back from a drive that has been rendered unmountable.

Recoverit author

Sue Wayne

staff Editor

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