No mountable disk systems is creating problem for you, don't worry as you can solve it easily now. Although the Mac systems are full of different features and you can perform different tasks through it, the storage capacity of it is limited. So some time or the other you will require an external drive for storing large and important files. But what if you are getting no mountable disk systems error when you are connecting the external drive to the Mac system. You will not be able to access the files that are saved in the drive. You must be looking for the causes of this error and how to recover data after no mountable disk systems error. The possible causes of this issue is that the drive is not properly connected or not getting enough power so you should check that. Another possibility is that the drive is corrupted and not responding, for this you have to format the drive. You can recover the data when the no mountable disk systems is fixed by using any backup. But when the backup is not available then you can use Mac data recover software. It simply scans and recover the files from the drive with ease. You should download the software and use it now.