Erase Process Has Failed Mac External Hard Drive

Posted by Tim to Mac Data Recovery Tips on April 19th, 2017

Cannot format external hard drive on Mac OS 10.5! If the formatting process on Mac OS 10.5 has failed but the drive has been successfully formatted on a PC or another computer previously, try following: Open the disk utility and select the external drive. Choose '1 Partition' from the volume scheme and then click on 'Options'. Jan 10, 2020 Maybe you want to troubleshoot some problems, repair the disk, do partitions, format the entire disk, update, and install OS X etc. All these are executed perfectly when you use an external boot volume to boot up your Mac. In this article, we are here with the detailed step by step guide on how to boot Mac from external hard drive easily.

Mac External Disk Drive

I have accidentally disconnected 3TB external hard drive without ejecting it first. Now when I run disk utility to repair disk, it says: 'Disk utility can't repair this disk. Back up as many of your files as possible, reformat the disk, and restore you backed-up files.' Is there anything else I can do to repair this external hard drive or recover the data?

Show All Drives. Select the main hard drive, not the volume then click on the Erase tab. A small window will appear now. As a name type any name you want and as format select Mac OS Extended Journaled, as a scheme select GUID Partition Map. Click the Erase button and wait for a while. Solve/Fix “Erase Process has Failed” While Erasing Partition for macOS on Disk Utility. Note: The first method below, is found by me and it may work on any other PC, though it was a Lenovo Z50-70 Laptop, I am somehow sure that it will work for you as well.

  • Disk Utility Error Message when formatting in MacBook Pro, iMac, Mac mini, Mac Pro, MacBook Air. There are 2 ways to really fix this problem.CODE you need fo.
  • There was an Apple Macintosh process that locked this external hard drive. The previous command shows all processes specific to the external hard drive. Now you want to kill all processes that are accessing the external hard drive: killall mds. You can use the Apple Macintosh “Activity Monitor” to end all processes as well.

It is a common problem that can cause data loss after external hard drive becomes corrupted. Sometimes, disk utility is able to repair corrupted external hard drive, but sometimes, disk utility cannot repair external hard drive which is caused by some reasons, such as file system corruption.

Two error types about disk utility cannot repair the disk

There are two error types about disk utility cannot repair the disk as below:

1. Disk utilily cannot repair this disk. You can still open or copy files on the disk, but you cannot save changes to files on the disk. Backup the disk and reformatt it as soon as you can:

2. Disk utilily cannot repair this disk. Back up as many of your files as possible, reformat the disk, and restore you backed-up files:

External hard drive becomes corrupted, we cannot access the data stored on it, if we click 'Erase' button, although we can access external hard drive after reformatting, but we will lose all data stored on it, if we don't reformat external hard drive, we cannot access it, so the first thing is to recover lost data from external hard drive after disk utility cannot repair external hard drive.

Recover lost data from external hard drive on Mac

M3 Data Recovery for Mac is the professional Mac data recovery software which can recover lost data from external hard drive that disk untility cannot repair, recover lost data from formatted, unmountable, uninitialized, corrupted drive, recover deleted or lost files on macOS Catalina 10.15/Mojave 10.14/High Sierra 10.13/10.12, Mac OSX 10.11/10.10/10.9/10.8 and supports HFS, HFS+, exFAT and FAT32 file systems.

Tutorial to recover lost data from external hard drive with M3 Data Recovery

Step 1: Download, install and then launch M3 Data Recovery for Mac on your Mac computer.

Mac Os X Can't Repair Disk External Hard Drive

Step 2: Select the external hard drive that disk utility cannot repair from the drop-down list.

Step 3: M3 Data Recovery for Mac is scanning lost data from the external hard drive

Step 4: Select the found files you expect to recover and then click Recover to recover lost data from external hard drive.

Reformat external hard drive that disk utility cannot repair

After data recovery is successfully done from external hard drive, please reformat and then it will be working again.

Step 1: Launch Disk Utility from Utilities.

Step 2: Click the icon for your external hard drive in the sidebar on the left.

Step 3: Click the Erase tab along the top of the window and enter the related information.


Step 4: Click the Erase button to start reformat operation.

About disk utility

Disk Utility is the name of a utility, created by Apple, for performing disk-related tasks on Mac OS. These tasks include:

Creation, conversion, backup, compression and encryption of logical volume images from a wide range of formats read by Disk Utility to .dmg or, for CD/DVD images:.cdr

Mount, unmount and eject disk volumes (including hard drive, removable device and disk images)

Enable or disable journaling

Verify a disk's integrity, and repair it if the disk is damaged

Erase, format, partition and clone disks

Secure deletion of free space or disk using a 35-pass Gutmann algorithm

Add or change partition table between Apple Partition Table and GUID Partition Table

Create, destroy and repair RAID sets

Restore volumes from Apple Software Restore (ASR) images

Check the S.M.A.R.T. status of a hard disk

Modifying this control will update this page automatically

Disk Utility User Guide

Disk Utility can fix certain disk problems—for example, multiple apps quit unexpectedly, a file is corrupted, an external device doesn’t work properly, or your computer won’t start up. Disk Utility can’t detect or repair all problems that a disk may have.

If you run First Aid on a disk, Disk Utility checks the partition maps on the disk and performs some additional checks, and then checks each volume. If you run First Aid on a volume, Disk Utility verifies all the contents of that volume only.

  1. In the Disk Utility app on your Mac, choose View > Show All Devices.

    Note: If you’re checking your startup disk or startup volume, restart your computer in macOS Recovery, select Disk Utility in the macOS Utilities window, then click Continue. If you check your startup volume (Macintosh HD), make sure you also check your data volume (Macintosh HD - Data).

  2. In the sidebar, select a disk or volume, then click the First Aid button .

    If Disk Utility tells you the disk is about to fail, back up your data and replace the disk—you can’t repair it. Otherwise, continue to the next step.

  3. Click Run, then click Continue.

    If Disk Utility reports that the disk appears to be OK or has been repaired, you’re done. You can click Show Details to see more information about the repairs. Otherwise, you may need to do one of the following.

    • If Disk Utility reports “overlapped extent allocation” errors, two or more files occupy the same space on your disk, and at least one of them is likely to be corrupted. You need to check each file in the list of affected files. Most of the files in the list have aliases in a DamagedFiles folder at the top level of your disk.

      • If you can replace a file or re-create it, delete it.

      • If it contains information you need, open it and examine its data to make sure it hasn’t been corrupted.

    • If Disk Utility can’t repair your disk, or you receive a report that the First Aid process failed, try to repair the disk or partition again. If that doesn’t work, back up as much of your data as possible, reformat the disk, reinstall macOS, then restore your backed-up data.

Mac Os X Cannot Repair The Disk External Hard Drive Windows 10

If your Mac has a Fusion Drive and you see a flashing question mark or alert, see the troubleshooting section of the Apple Support article About Fusion Drive, a storage option for some Mac computers.

If you continue to have problems with your disk or it can’t be repaired, it may be physically damaged and need to be replaced. For information about servicing your Mac, see Find out how to service or repair your Mac.

Mac Os X Cannot Repair The Disk External Hard Drive Driver

See alsoErase and reformat a storage device in Disk Utility on MacAdd, delete, or erase APFS volumes in Disk Utility on MacPartition a physical disk in Disk Utility on Mac

The Disk Utility on Mac is a very useful system tool for fixing specific disk problems. For example, you can run a disk check when your apps quit simultaneously, an external drive is not working properly, or your Mac won’t startup. Disk Utility will check the health of your hard drive and repair any disk errors if possible.

Disk Utility usually works smoothly, but there are times when frustrating errors occur and prevent the process from being completed. One of the common errors encountered when using Disk Utility is the “Couldn’t Unmount Disk” error. When this error pops up, any attempted task gets stopped right in its tracks.

What is the “Couldn’t Unmount Disk” Error on Mac?

The “Couldn’t Unmount Disk” error can happen during formatting, partitioning, disk verification and repair, or any task that the Disk Utility undertakes. What makes this error frustrating is that there is usually very little to no additional information provided by the error message, making it more challenging to resolve the problem, And based on the error message, it is even harder to determine what the problem is all about.

Here are some variations of the error message that Mac users encounter, depending on the process being executed when the error happened:

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  • Disk Erase failed.
    Disk Erase failed with the error:
    Couldn’t Unmount Disk.
  • Partition failed
    Partition failed with the error:
    Couldn’t Unmount Disk.
  • Disk Utility stopped verifying (letter of the hard disk)
    Couldn’t Unmount Disk.
  • Volume Erase failed
    Volume Erase failed with the error:
    “Couldn’t Unmount Disk”.

Once this pops up, the current process gets halted and could no longer proceed, affecting any troubleshooting process or disk repair you might be doing.

Erase Process Has Failed Mac External Hard Drive

What Causes the “Couldn’t Unmount Disk” Error in Disk Utility for Mac?

When your Mac is getting the “Couldn’t Unmount Disk” error when using the Disk Utility, it is possible that the boot drive cannot be modified because it is being used by some process or an application. For example, a file from the disk you are trying to erase could be open, which means that you can’t proceed with the erasing unless all the files are closed.

Another possible reason is the presence of malware. When a malicious software is running in the background and wreaking havoc on your Mac, you might get the “Couldn’t Unmount Disk” error when you try to do something with your hard drive. This is because the malware might be making changes to your hard drive without you knowing it.

Other factors you should look into include corrupted system files, bad hard drive sectors, or insufficient permissions. Whatever the reason is, resolving this “Couldn’t Unmount Disk” error should be your priority because it might lead to further disk damage or other hard drive issues.

How to Fix the “Couldn’t Unmount Disk” Error on Mac

If your Mac is getting the “Couldn’t Unmount Disk” error, don’t worry because there are several ways to handle this problem. But before you do so, here are some of the basic troubleshooting you should take care of first:

  • Close all applications and files before attempting the repair.
  • Make sure you have enough permissions to read and write to the drive you want to modify.
  • Run a scan to check for the presence of malware. Delete any malicious software detected using your antivirus and delete all related files.
  • Disable your security software after running the scan because it might prevent the processes from pushing through.
  • Declutter your system by cleaning up your computer with a Mac cleaning tool. This should fix any errors related to corrupted junk files or cached data on your Mac.
  • Restart your computer.

Once you’ve completed the steps above, you can now proceed with the main solutions:

Solution #1: Use a USB Boot Drive to Repair the Hard Drive.

If “Couldn’t Unmount Disk” error occurs when you are trying to modify the boot drive, the easiest solution is to boot your Mac using another drive, and then run Disk Utility from that disk. You can use an installation drive or a recovery drive, as long as it is bootable and it is separate from the primary boot disk where your macOS is installed.

Here are the steps you need to follow to resolve this error using a USB boot drive:

  1. Connect the USB boot drive to your Mac, then reboot.
  2. While restarting, hold down the Option key button and choose the attached boot drive.
  3. In the boot menu, choose Disk Utility.
  4. Click First Aid at the top menu to verify the disk.
  5. Once your disk has been verified, you can then proceed with the task you were trying to perform when the error occurred.

Solution #2: Use the Recovery Partition.

If the “Couldn’t Unmount Disk” error message appears when doing First Aid on your disk or formatting a non-boot disk, the first solution will not work. If this is the case, you can try resolving the error using Recovery Partition.

Here’s how to do it:

  1. Reboot your Mac.
  2. While booting up, hold down the Option key to boot using the Recovery Partition.
  3. Next, click on Disk Utility from the boot menu.
  4. Click First Aid to verify the disk or select Erase to format the disk if needed.

Keep in mind that this method will only work if the disk that is throwing the error is not the same as the primary boot partition where the Recovery Partition is saved.

Solution #3: Use Command Prompt to Force Unmount the Disk.

If the above methods don’t work and your disk is pretty stubborn, you can attempt to fix this error by forcing to unmount the disk using commands.

To do this, follow the steps below:

  1. Launch Terminal by navigating to Finder > Go > Applications > Utilities.
  2. In the Terminal window, type in the following command: diskutil list
  3. This will list down all the available disks on your Mac.
  4. Look for the disk that you want to force unmount and take note of the number of the drive.
  5. Type in this command next: sudo diskutil unmountDisk force /dev/diskx
  6. Replace /dev/diskx with the disk number of the drive you want to unmount (for example, dev/disk1).
  7. Wait for the process to be completed.

How To Erase And Reformat An External Hard Drive For Mac

Solution #4: Use a Third-Party App.

If you don’t want to go through the trouble of booting using the USB boot drive or typing in commands in the Terminal, you can use a third-party tool instead. There are a lot of repair utilities to help you deal with this “Couldn’t Unmount Disk” error. These utilities can also be used to format, partition, erase, or modify your disk. Just make sure to choose a reliable app that can help you perform these tasks without any error.


Erase Process Has Failed Mac External Hard Drive Doesn T Show Up

The Disk Utility on macOS is a useful tool for fixing any disk-related issues or performing tasks that involve the hard drive. But this tool is not impregnable. Flaws, such as the “Couldn’t Unmount Disk” error, can happen from time to time. When this happens, simply follow the solutions listed above and you’ll be good to go.