Notes

Comparison with SATA

There is little physical difference between SAS and SATA.[3]

1-Systems identify SATA devices by their port number connected to the host bus adapter or by their universally unique identifier (UUID), while SAS devices are uniquely identified by their World Wide Name (WWN).
2-SAS protocol provides for multiple initiators in a SAS domain, while SATA has no analogous provision.[3]
3-Most SAS drives provide tagged command queuing, while most newer SATA drives provide native command queuing.[3]
4-SATA uses a command set that is based on the parallel ATA command set and then extended beyond that set to include features like native command queuing, hot-plugging, and TRIM. SAS uses the SCSI command set, which includes a wider range of features like error recovery, reservations and block reclamation. Basic ATA has commands only for direct-access storage. However SCSI commands may be tunneled through ATAPI[3] for devices such as CD/DVD drives.
5-SAS hardware allows multipath I/O to devices while SATA (prior to SATA 2.0) does not.[3] Per specification, SATA 2.0 makes use of port multipliers to achieve port expansion, and some port multiplier manufacturers have implemented multipath I/O using port multiplier hardware.
6-SATA is marketed as a general-purpose successor to parallel ATA and has become[update] common in the consumer market, whereas the more-expensive SAS targets critical server applications.
7-SAS error-recovery and error-reporting uses SCSI commands, which have more functionality than the ATA SMART commands used by SATA drives.[3]
8-SAS uses higher signaling voltages (800–1,600 mV for transmit, and 275–1,600 mV for receive[clarification needed]) than SATA (400–600 mV for transmit, and 325–600 mV for receive[clarification needed]). The higher voltage offers (among other features) the ability to use SAS in server backplanes.[3]
Because of its higher signaling voltages, SAS can use cables up to 10 m (33 ft) long, whereas SATA has a cable-length limit of 1 m (3.3 ft) or 2 m (6.6 ft) for eSATA.[3]
9-SAS is full duplex, whereas SATA is half duplex. The SAS transport layer can transmit data at the full speed of the link in both directions at once, so a SCSI command executing over the link can transfer data to and from the device simultaneously. However, because SCSI commands that can do that are rare, and a SAS link must be dedicated to an individual command at a time, this is generally not an advantage