Hello KQR, computers have 3 SATA modes so you can choose from:
• IDE mode, in which neither AHCI nor RAID is enabled.
• AHCI mode, also called SATA mode, has AHCI enabled but not RAID
• RAID mode, which is the same as AHCI mode but with RAID support.
If you want to create a RAID array on your system, you must have RAID mode enabled on BIOS. RAID won't work in AHCI mode.
Sometimes, when you change the SATA mode from AHCI to RAID it would be necessary to reinstall the operating system.