Note:
Repeat this for each volume used for the MySQL instance.
Microsoft Windows - Press the Win + R keys to open Run, type diskmgmt.msc into Run, and click/tap on OK to open Disk Management. Right click or press and hold on the drive (ex: "MySQL_Base") you want to unmount, and click/tap on Change Drive Letter and Paths.
Select the mount point and click on the Remove button and then the OK button.
Linux - In a terminal execute the umount command:
umount /var/lib/mysql