SAS LastModified: Tuesday, September 07, 2004
(pronounced as separate letters) Short for Serial Attached SCSI, an evolution of parallel SCSI into a point-to-point serial peripheral interface in which controllers are linked directly to disk drives. SAS is a performance improvement over traditional SCSI because SAS enables multiple devices (up to 128) of different sizes and types to be connected simultaneously with thinner and longer cables; its full-duplex signal transmission supports 3.0Gb/s. In addition, SAS drives can be hot-plugged. In topologies with more than two connected devices, SAS calls for the use of expander devices to allow for more than one host to connect to more than one peripheral. SAS devices can communicate with both SATA and SCSI devices (the backplanes of SAS devices are identical to SATA devices). A key difference between SCSI and SAS devices is the addition in SAS devices of two data ports, each of which resides in a different SAS domain. This enables complete failover redundancy as if one path fails, there is still communication along a separate and independent path.
Introduction to Serial Attached SCSI An overview of the architecture and features of Serial Attached SCSI. (pdf) Serial Attached SCSI Tutorials Provided by SCSI Trade Association, these tutorials examine the different layers of the SAS standard.	related categories: Buses Miscellaneous Standards Peripheral Devices related terms: backplane controller interface peripheral device SCSI Serial ATA