The standard operating mode/protocol used by SATA controllers to communicate with storage devices. It was designed in the mid-2000s primarily for traditional spinning hard drives. Key traits:
- Supports native command queuing
- Allows hot-swapping
- Limited to one queue with only 32 commands deep
AHCI is the language that SATA controllers speak. It works fine for HDDs and early SATA SSDs, but it severely limits performance with modern NVMe-class flash storage because it can’t handle thousands of parallel operations like NVMe can.