SAS (Serial Attached SCSI)
It is also possible to use attached to a SAS controller through the S- ATA Tunneling Protocol (STP) and S- ATA drives. In contrast to point-to- SCSI point connections are used in SAS, there is thus a device is used per connection. By special expander but a so-called storage domain be established ( similar to the known world from the network switches).
This allows a variety of drives to a controller with a lower number of ports to operate. SAS drives often have two SAS ports. This can either lead to aggregation ( increase in data throughput) or can be used to connect the hard drive to two different host adapter. By using a hard drive on two different host adapters, redundant systems can be realized. Since 2013 data transfer rates of up to 12 Gbit / s are possible with the third version of the protocol. The previous version from 2009, made ??possible by trunking also 12Gbit / s ( per-port 6Gb / s) and is currently the most commonly used variant.
The plugs and cables are similar to those of the S- ATA standards, but in a slightly different form. SAS devices can not be connected to the S- ATA cable, but probably S- ATA devices to SAS cable, which is done by design by the backward compatibility. In addition, special cables are available eg specifically designed for cable bundling.