Starting Raid 1 in Wondiws 10

A client of mine has a Dell workstation that came with Windows 7. He upgraded to Windows 10 and now wants me to Install Raid 1 on the machine. This model does have a hardware raid controller, but I have the impression that if I set up that raid, I''ll have to wipe out the original drive to create a new Raid 1 with the original and new drives.  Am I correct about that? Windows 10 has a feature called Storage Space which can be configured as a Raid 1, but I believe that configures two ADDITIONAL drives as a Raid1 which does not include the original drive, right?

That leaves only the disk  management console in which I know I can add an additional drive to the original. But I have an issue with this function. In order to add a new drive to the original to form a Raid 1, both drives have to be dynamic. The original drive has several partitions, two of which are Recovery partitions and the third is the C; drive.  When I try to convert the drive to dynamic, I get an error message " The operation could not be completed. There is not enough space to complete the request." I know there is lots of space on the C: drive partition. Exactly how much space do I need, or is it the existence of the Recovery partitions that is preventing the conversion?

If there is another diagnosis and/or solution to this issue, I'd like to know. Thanks for any help.