How you access a secondary drive on your dedicated server depends on which operating system you are using. If you are using Linux®, you can use SSH to access the drive. If you are using Windows®, you can use Remote Desktop to connect to the server, and then use My Computer to browse to the secondary drive.
You can also access the secondary drive using FTP. To do this, you need to use SSH or IIS to create an FTP user, and then configure the user to access the secondary drive.
You cannot access the secondary drive by using a control panel. The control panel only uses the drive on which it is installed.
If your secondary drive is mirrored using RAID, then you do not need to access the drive. When a drive is mirrored, all content from the primary drive is automatically duplicated on the secondary drive.