Lenovo ThinkServer RD240 MegaRAID SAS Software User Guide - Page 27

1.2 Serial-attached SCSI Device Interface SAS is a serial, point-to-point, enterprise-level device interface that leverages the proven SCSI protocol set. SAS is a convergence of the advantages of SATA II, SCSI, and Fibre Channel, and is the future mainstay of the enterprise and high-end workstation storage markets. SAS offers a higher bandwidth per pin than parallel SCSI, and it improves signal and data integrity. The SAS interface uses the proven SCSI command set to ensure reliable data transfers, while providing the connectivity and flexibility of point-to-point serial data transfers. The serial transmission of SCSI commands eliminates clock-skew challenges. The SAS interface provides improved performance, simplified cabling, smaller connectors, lower pin count, and lower power requirements when compared to parallel SCSI. SAS controllers leverage a common electrical and physical connection interface that is compatible with Serial ATA technology. The SAS and SATA II protocols use a thin, 7-wire connector instead of the 68-wire SCSI cable or 26-wire ATA cable. The SAS/SATA II connector and cable are easier to manipulate, allow connections to smaller devices, and do not inhibit airflow. The point-to-point SATA II architecture eliminates inherent difficulties created by the legacy ATA master-slave architecture, while maintaining compatibility with existing ATA firmware. 1.3 Serial ATA II Features The SATA bus is a high-speed, internal bus that provides a low pin count, low voltage level bus for device connections between a host controller and a SATA device. The following list describes the SATA II features of the RAID controllers: • Supports SATA II data transfers of 3.0 Gbits/s • Supports STP data transfers of 3.0 Gbits/s • Provides a serial, point-to-point storage interface • Simplifies cabling between devices Serial-attached SCSI Device Interface 1-3