Hi
it seems that there might be an issue with the drive letter assignment or visibility of the D drive after restoring the system through the mirror on Windows Server 2016. Here are a few steps you can try to resolve the issue:
Open Disk Management: Press Win + X and select "Disk Management" from the menu to open the Disk Management console.
Check for the missing partition: In the Disk Management window, look for the partition that corresponds to the missing D drive. It might appear as unallocated space or have a different drive letter assigned.
Assign a drive letter: If you see the partition without a drive letter assigned, you can assign a drive letter to it. Right-click on the partition, select "Change Drive Letter and Paths," and then click "Add." Choose a suitable drive letter, such as D, and click "OK."
Refresh the Explorer: After assigning the drive letter, the D drive should become visible in File Explorer. If it doesn't appear immediately, try refreshing the Explorer window by pressing F5 or right-clicking and selecting "Refresh."
Check for conflicts: If the D drive is still not visible, there might be a conflict with another drive or partition that already has the D drive letter assigned. In Disk Management, ensure that no other partitions or removable drives are using the same drive letter. If necessary, you can change the drive letter of those conflicting partitions to make room for the D drive.