(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 3.0
Gb/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.
