SAS – Serial-Attached SCSI. SCSI is the Small Computer Systems Interface and SAS is a point-to-point connectivity protocol. It replaced an earlier parallel SCSI system. In a SAS system there is an initiator to originate data transfer requests, a target to receive them, a connection such as a cable to carry them, and possible expanders that enable multiple SAS end devices to connect to a single initiator port.
There are different generations of SAS, each faster than the preceding generation;
- SAS-1: 3.0 Gbit/s, introduced in 2004,
- SAS-2: 6.0 Gbit/s, available since February 2009,
- SAS-3: 12.0 Gbit/s, available since March 2013,
- SAS-4: 22.5 Gbit/s called ’24G’, standard completed in 2017,
- SAS-5: 45 Gbit/s is being developed.