Can't mount external drive after erasing error with Disk Utility

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Level 4

1,557 points

Can't mount external drive after erasing error with Disk Utility

Hi, guys.

Last Sunday, I tried to erase an external hard drive using Disk Utility. I chose to format it as FAT32 (MS-DOS (FAT)) and I selected the first level of Security Options.

During the process of writing zeros, the Disk Utility had an error and didn't finish correctly.

Since then, I can't neither mount the drive, nor access it via Terminal.

The drive:

Does NOT show up in Disk Utility (not even as unmounted);
Does show up on System Report under USB;
Does show up on Terminal Diskutil List.

I included the Terminal commands I tried and the resultas I got as additional text.

It's important to highlight I know nothing about Terminal commands and everything I used I took from technical posts on forums.

My Mac:

MacBook Pro (13-inch, 2018, Four Thunderbolt 3 Ports), 2,3 GHz Quad-Core Intel Core i5, 8 GB 2133 MHz LPDDR3

The External Drive:

USB to Serial-ATA bridge:

Product ID: 0x0c31

Vendor ID: 0x1bcf (Sunplus Innovation Technology Inc.)

Version: 1.0f

Serial Number: ...

Speed: Up to 480 Mb/s

Manufacturer: Sunplus Innovation Technology.

Location ID: 0x14100000 / 6

Current Available (mA): 500

Current Required (mA): 2

Extra Operating Current (mA): 0

Media:

MK7559GSXF:

Capacity: 750,16 GB (750.156 bytes)

Removable Media: No

BSD Name: disk3

Logical Unit: 0

Partition Map Type: GPT (GUID Partition Table)

S.M.A.R.T. status: Verified

USB Interface: 0

Volumes:

EFI:

Capacity: 209,7 MB (209.715 bytes)

File System: MS-DOS FAT32

BSD Name: disk3s1

Content: EFI

Volume UUID: 0E239BC6...

UNTITLED:

Capacity: 749,29 GB (749.294 bytes)

File System: MS-DOS FAT32

BSD Name: disk3s2

Content: Microsoft Basic Data

Volume UUID: B...

I'd appreciate any help you guys could give me.

Thanks in advance.

JP

Terminal attempts and results

Posted on Jul 21, 2020 2:17 PM

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Answer 1

Jul 21, 2020 6:19 PM in response to JP Ellery

Sometimes when a drive gets into a weird or unusual state macOS will have problems erasing it. When that happens I will zero out the first part of the drive to destroy the partition table and early parts of the drive. Using "disk3" as an example from your post the command would be:

sudo  dd  if=/dev/zero  of=/dev/disk3   bs=100m  count=10

Make sure to replace "disk3" with the correct drive identifier for your external drive. Usually after this Disk Utility will be able to partition & erase the drive properly assuming the drive is healthy. For information about this command and the options you can read the man pages by using the following command (use arrow keys or scroll wheel to scroll up & down and press "q" to quit):

man  dd

To check the health of the external drive you can use DriveDx. You will need to install a special USB driver in order for DriveDx to be able to access the external drive's health information. Even with this special USB driver DriveDx may not be able to access the drive's health information because some external drive's USB controllers don't allow the necessary communication. If you can access the drive's health information, then post the complete DriveDx report here using the "Additional Text" icon which looks like a piece of paper.

I've had some issues with external USB3 drives on my Mac and had to resort to using a good quality powered USB3 hub to act as a filter & buffer to prevent issues. If you are already using a USB hub, then maybe your hub is defective so try connecting the drive directly to the computer. You may also want to try using another USB port and cable.

Have you tried rebooting your computer?

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Answer 2

Jul 22, 2020 4:34 PM in response to JP Ellery

It is starting to sound like you have a failing hard drive. Pull the drive from the enclosure and use a USB to SATA Adapter so you can check the health of the hard drive.

https://www.startech.com/HDD/Adapters/USB-3-SATA-adapter-cable-with-UASP~USB3S2SAT3CB

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Answer 3

JP Ellery Author

Level 4

1,557 points

Jul 22, 2020 6:16 AM in response to HWTech

Hello, HWTech!

Once again, thank you for taking your time to help me.

Unfortunately, no candy for me.

diskutil  unmountDisk  disk2                             
Unmount of all volumes on disk2 was successful
sudo  dd  if=/dev/zero  of=/dev/disk2   bs=100m  count=10
dd: /dev/disk2: Resource busy

Regarding the case itself, yes, it has screws and I can swap drives inside it at will. Actually, this drive I'm trying is an old MacBook Pro drive I replaced by a SSD a while back. The down side is that I don't have the required adapters to plug it direct to a mother board.

If you could think of anything else, I'd be very grateful. But I know I've been asking too much already.

Thanks in advance for your help.

JP

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Answer 4

JP Ellery Author

Level 4

1,557 points

Jul 21, 2020 7:30 PM in response to HWTech

Hello, HWTech!

Thanks a lot for your reply.

Unfortunately, it didn't solve the problem.

I get the following return:

sudo  dd  if=/dev/zero  of=/dev/disk2   bs=100m  count=10
dd: /dev/disk2: Resource busy

This time, I connected only the drive that has the issue and I connected it through a powered USB hub as suggested.

Regarding DriveDx, please, see the attached image.

Do you think there's anything else I can try before saying bye-bye to this drive?

Thanks a lot for your time.

JP

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Answer 5

Jul 21, 2020 8:04 PM in response to JP Ellery

That is unfortunate about the enclosure not allowing DriveDx to access the drive's health information. If the enclosure has screws then you could disassemble it to remove the hard drive so you could use a USB to SATA Adapter (assuming the external drive doesn't wire the USB cable or USB port to the hard drive's Logic Board.

In order to zero out the drive with "dd" you first need to unmount all volumes on the drive. Using the information in your most recent post as a guide you can use the following command (again replacing "disk2" with the actual current drive identifier for the external drive):

diskutil  unmountDisk  disk2

Then run the "dd" command.

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Can't mount external drive after erasing error with Disk Utility

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