Serial Attached SCSI - Comparison With SATA

Comparison With SATA

There is little physical difference between SAS and SATA.

• 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).
• SAS protocol provides for multiple initiators in a SAS domain, while SATA has no analogous provision.
• Most SAS drives provide tagged command queuing, while most newer SATA drives provide native command queuing, each of which has its pros and cons.
• 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. Basic ATA has commands only for direct-access storage. However SCSI commands may be tunneled through ATAPI for devices such as CD/DVD drives.
• SAS hardware allows multipath I/O to devices while SATA (prior to SATA 3Gb/s) does not. Per specification, SATA 3Gb/s makes use of port multipliers to achieve port expansion. Some port multiplier manufacturers have implemented multipath I/O using port multiplier hardware.
• SATA is marketed as a general-purpose successor to parallel ATA and has become common in the consumer market, whereas the more-expensive SAS targets critical server applications.
• SAS error-recovery and error-reporting use SCSI commands which have more functionality than the ATA SMART commands used by SATA drives.
• SAS uses higher signaling voltages (800–1600 mV TX, 275–1600 mV RX) than SATA (400–600 mV TX, 325–600 mV RX). The higher voltage offers (among other features) the ability to use SAS in server backplanes.
• Because of its higher signaling voltages, SAS can use cables up to 10 m (33 ft) long, SATA has a cable-length limit of 1 m (3 ft) or 2 m (6.6 ft) for eSATA.