Based on the description you provided, the result of the process you did is an expected behavior from Intel® Rapid Storage Technology.
This is because at the time that you formatted the HDD, it was still under the Array volume. Intel® Rapid Storage Technology will start rebuilding the Array from the existing HDD in the system. This process is to copy another exact image that is in the Hard Disk Drive into the new added Hard Disk Drive and since the first one was formatted, the new one will have the same data based on the RAID 1 configuration.
Thanks for the answer. But one question, shouldn't the Intel RST copy the data to the new formatted drive and not the other way around? Why did the program copied the data from the empty drive (the formatted drive) to the drive with all the data (the drive overwritten)? I took out one drive and once I formatted it, then I put it back in the same place. Was the Intel RST bad configured? Maybe I had to tell Intel RST which drive should it take the data from.
The Intel® Rapid Storage Technology will start rebuilding the Volume from the HDD that is connected to the system at that moment.
This is the reason why it deleted everything. The HDD that was formatted was still configured as a RAID so the Intel® Rapid Storage Technology automatically will start copying the information in the Hard Disk Drive to the new Driver that has been connected.