What are the advantages and characteristics of the SAS interface?

SAS (Serial Attached SCSI) is Serial Attached SCSI. It is a new generation of SCSI technology. It is the same as the popular SerialATA (SATA) hard disk. It adopts serial technology to obtain higher transmission speed and improves by shortening the connection line. interior space, etc. So what are its advantages and features?

The interface technology of SAS is backward compatible with SATA. Specifically, the compatibility of the two is mainly reflected in the compatibility of the physical layer and the protocol layer. At the physical layer, the SAS interface is fully compatible with the SATA interface, and SATA hard drives can be directly used in the SAS environment. In terms of interface standards, SATA is a sub-standard of SAS.

Therefore, the SAS controller can directly control the SATA hard disk, but the SAS cannot be directly used in the SATA environment, because the SATA controller cannot control the SAS hard disk; at the protocol layer, SAS consists of 3 types of protocols, depending on the connection The device uses the corresponding protocol for data transmission.

Among them, Serial SCSI Protocol (SSP) is used to transmit SCSI commands; SCSI Management Protocol (SMP) is used to maintain and manage connected devices; SATA Channel Protocol (STP) is used to transmit data between SAS and SATA. Therefore, with the cooperation of these three protocols, SAS can be seamlessly combined with SATA and some SCSI devices.

In the system, each SAS port can connect up to 16,256 external devices, and SAS adopts a direct point-to-point serial transmission method with a transmission rate of up to 3Gbps. It is estimated that there will be high-speed interfaces of 6Gbps or even 12Gbps in the future.

The interface of SAS has also been greatly improved. It provides 3.5-inch and 2.5-inch interfaces at the same time, so it can meet the needs of different server environments.

SAS relies on SAS expanders to connect more devices. The current expanders are mostly 12 ports. However, according to the product R&D plan of board manufacturers, 28 and 36 port expanders will be introduced in the future to connect SAS devices and host devices. Or other SAS expanders.

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