Hello WHeyl
Thank you for posting in the Intel Community.
Bear in mind Intel® Rapid Storage Technology (Intel® RST) is not to free up disk space on the system, this software is developed to create, configure, administrate and monitor the RAID array on the system, if you have 2 HDDs according to the picture you have shared the RAID level configured is 0 that means at this point the previous data on the system has been deleted and there is no way to get it back.
NOTE: Before trying anything with RAID controllers you should have a data backup.
Hope this helps.
Regards,
Leonardo C.
Intel Customer Support Technician
Under Contract to Intel Corporation