A SAS controller is a device that manages the communication between a computer's central processing unit (CPU) and its storage devices using the Serial Attached SCSI (SAS) protocol. It enables efficient data transfer and ensures that multiple storage devices can be connected and accessed simultaneously. SAS controllers are commonly used in servers and high-performance computing environments, where speed and reliability are crucial. They support various storage configurations, including hard disk drives (HDDs) and solid-state drives (SSDs), allowing for flexible storage solutions tailored to specific needs.