How to recover unmountable volumes on Mac

A Mac’s disk is usually divided into separate sections: partitions and, within them, logical volumes.

On a Mac, repeated attempts with Disk Utility can make the case worse. If the files matter, see Bot’s hard drive recovery, which starts with a free diagnosis.

This lets you keep different kinds of data separate.

The great advantage of this system is that the system files on the startup volume are kept apart from your other data, which helps the Mac start up smoothly.

However, volumes sometimes become unmountable, and when this happens to the startup volume, the Mac can’t start.

This is a critical situation: the data stored on the disk becomes inaccessible, and there is a real risk of losing it.

If a volume on your Mac has become unmountable, read this article to find out what may have caused it and how to try to solve the problem without putting your data at risk.

01What are unmountable volumes?

Volumes are the logical space in which data, system files and other information are stored on macOS.

When a Mac starts up, macOS mounts the file systems of the local volumes.

In other words, a volume is mounted when macOS can read and write data on it.

Mounting is the process in which macOS reads the information about a volume so that it can access its storage space to read and write data.

02Common reasons why a volume becomes inaccessible

Knowing what causes the problem helps you decide how to deal with a disk that has become unmountable on your Mac.

The main ones are:

File system corruption

If the structure of the file system (APFS or HFS+) is damaged, the data on the volume becomes inaccessible to the system.

File system corruption can be caused, for example, by an interrupted or incorrect format, reformat or file system conversion, or by disconnecting a drive without ejecting it first.

Virus or malware infection

If the disk is infected with a virus, the infection can cause system files to become corrupted.

As a result, the volume may become unmountable.

Operating system malfunction

The volume may also become unmountable because the operating system has crashed or is not working properly.

03How to recover data from an unmountable Mac disk

To recover your data from an unmountable disk on your Mac, you have two options:

• Use data recovery software: this requires some technical knowledge and familiarity with the process, and if it is done incorrectly it can make things worse and cause permanent data loss. If the disk makes noises or has physical problems, don’t use software at all.
• Use a professional data recovery service: this gives you a better chance of recovering your data and minimizes the risk of further damage to your device.

If you want to try recovering data from the unmountable disk with software, follow these steps:

Step 1

Choose a data recovery program and install it on a different drive from the one you want to recover, so that nothing is written to it. In this list, you’ll find some of the best free data recovery tools.

Then run the program and select the volume you want to recover data from.

Step 2

The tool will start scanning the volume to look for recoverable data. This may take a while, so wait until it finishes.

Step 3

After the scan, you’ll see the recoverable files the program has found. Select the ones you want and start the recovery.

Step 4

Choose where to save the recovered files. Always save them to a different drive from the one the lost files were on.

If the program can’t recover your files, you’ll need to turn to a data recovery company such as Bot.

04How do I repair an unmountable disk on my Mac?

When a volume becomes unmountable, the first thing most people think of is using Disk Utility to repair it.

Disk Utility has a built-in feature called First Aid, which checks the volume for errors and tries to repair them.

However, First Aid has its limits. Firstly, it often can’t repair the errors.

Secondly, because it writes to the disk, it can make things worse if the disk is failing, reducing the chances of recovering your data. If the data is important and you don’t have a backup, recover it first.

Method 1: Use Disk Utility

Disk Utility can fix some disk problems, so you can try it when a volume on your Mac won’t mount, as long as your data is backed up or the disk shows no signs of physical failure.

To run it:

• Open the Apple menu;
• Click “Restart”;
• On a Mac with an Intel processor, immediately press and hold “Command + R” (on a Mac with Apple silicon, shut it down and then press and hold the power button until the startup options appear);
• Keep holding the keys until you see the Apple logo;
• Click “Disk Utility” and then “Continue”;
• Choose “View” and then “Show All Devices”;
• In the sidebar, choose the volume you want to repair;
• Click “First Aid”;
• Disk Utility may warn you that the disk is about to fail. In that case, don’t run any repairs: back up your data to another drive first;
• If you don’t get this warning, click “Run”;
• Disk Utility will then tell you whether the volume has been repaired;
• If Disk Utility reports that it couldn’t repair the volume, don’t format it yet: recover your data first, with software or a lab, and only then erase the disk.

If Disk Utility reports that the volume was repaired, you can usually use the drive again, but keep a backup up to date, because the problem may come back.

Method 2: Erase (format) the drive

If First Aid couldn’t repair the volume and your data is already safe, you can erase (format) the drive that had the mount error.

This usually gets the drive working again, but remember that it erases all the data stored on the volume, so only do it once your data has been recovered or backed up.

To do this:

• Go to “Utilities” and open “Disk Utility”;
• In the sidebar, select the disk you want to erase;
• Click “Erase” and choose the name, format and scheme;
• Click the “Erase” button to confirm, and the formatting will begin.

05Conclusion

Volumes let you store data separately, keeping your files apart from the startup volume.

However, in cases of file system corruption, operating system malfunction or virus infection, these volumes can become unmountable.

In these cases, you can either use data recovery software (at the risk of damaging the data further and losing your files for good) or leave the recovery to a specialized company, which increases your chances of getting your data back without damaging your device.

Here at Bot, we have extensive experience in data recovery.

Our highly trained specialists recover data in a particle-controlled environment, to protect your drive.

We also offer 24/7 support on our social networks, where we’re happy to help and answer your questions.

Trust those with more than 200,000 cases: Start your data recovery with us now!