SAS
(1) (SAS Institute Inc., Cary, NC, www.sas.com) A software company that specializes in data warehousing and decision support software based on the SAS System. Founded in 1976, SAS is one of the world's largest privately held software companies. See SAS System.
(2) (Serial Attached SCSI) A serial version of the SCSI interface, which has been parallel since its inception in 1986. Ratified by ANSI in 2003 as the next-generation SCSI technology, SAS is a point-to-point architecture that uses a disk controller (host bus adapter) with four or more channels that operate simultaneously. Each full-duplex channel, known as a SAS port, transfers data at 3 Gbps in each direction with 6 Gbps scheduled for the next version. SAS also supports Serial ATA (SATA) drives, which can be mixed with SAS drives in a variety of configurations.
SAS Protocols
The Serial SCSI Protocol (SSP) is used for SAS-only drives, while the Serial ATA Tunneling Protocol (STP) is used to support SATA drives. When Expanders are used, the Serial Management Protocol (SMP) is employed. See SATA and SCSI. See also SSA.
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| Huge Scalability |
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| SAS channels (ports) can each connect to a single drive or collectively to an expander switch. Expanders can connect up to 128 devices, whether they be host bus adapters or drives. One Fanout Expander can be used to connect Edge Expanders, and one system would be capable of supporting a total of 16,256 drives. |
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| Dual Ports for Fault Tolerance |
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| SAS drives use the same form factor as Serial ATA (SATA) for the cable connector, but add a second port for connection to two controllers or expanders for fault tolerance. |
SAS