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Hello, ntoniraid. Thank you very much for taking the time to reach the Intel Communities Team. I will do my best to assist you further.
In this case, since you are having a RAID1 (mirroring) on your system, both disks should have the same information. Then, since the array was degraded, when you start the rebuilding process the information from the SATA disk, which is currently not in the array; should be deleted and replaced with the information of the disk that is currently in the degraded RAID array.