I have a Western Digital 2TB hard drive where I stored most of my files. One day, when I connect the drive to the Mac I can see it in disk utility as "not mounted". I try to run "Verify disk" it will fail to verify and say that the disk needs to be repaired. Then I try to repair it, it will start the process and then give me an error saying that the drive can not be repaired. How should I recover the data from this hard drive?
This symptom means the file system has been damaged, but the lost data can be recovered, you just need to find a professional Mac data recovery software to recover data from unmountable external hard drive. After data recovery is done successfully, use the disk utility to format the unmounted external hard drive, then the external hard drive will work as normal.
M3 Mac Data Recovery is the professional Mac data recovery software which can recover data from unmountable external hard drive in macOS 10.13/10.12 and Mac OSX 10.11/10.10/10.9/10.8/10.7 and supports HFS, HFS+, exFAT and FAT32 file systems.
Tutorial to recover lost data from not mounted external hard drive
Step 1: Download, install and then launch M3 Mac Data Recovery on your Mac computer.
Step 2: There are several options on M3 Mac Data Recovery home window, please select "In a specific volume" option and then choose the unmounted volume from the drop-down volume list or select "In a specific hard drive" and then choose the unmounted external hard drive from the drop-down hard drive list.
Step 3: M3 Mac Data Recovery is scanning lost data from unmountable external hard drive
Step 4: Select the found files you expect to recover and then click Recover to recover lost data from unmountable external hard drive.
Fix the issue of "External hard drive is not mounted in disk utility"
After data recovery is successfully done, please reformat this unmounted external hard drive, then this unmounted external hard drive will work as normal.
Step 1: Launch Disk Utility from Utilities.
Step 2: Click the icon for your unmounted 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.