SAS

SAS, or Serial Attached SCSI, is a computer bus technology primarily designed for transfer of data to and from data storage devices such as hard drives, CD-ROM, DVD, tape drives, and similar devices. It is designed for the corporate and enterprise market as a replacement for parallel SCSI, allowing for much higher speed data transfers, and is backward compatible with SATA drives. SATA drives may be connected to SAS controllers, but SAS drives may not be connected to SATA controllers.

SAS vs. SATA
SATA follows the ATA command set and thus only supports hard drives and CD/DVD drives. In theory, SAS also supports numerous other devices including scanners and printers. However, this advantage could also be moot, as most such devices have also found alternative paths via such buses as USB, IEEE 1394 (FireWire), and Ethernet. SATA is marketed as a general-purpose successor to Parallel ATA and is now common in the consumer market, while the more expensive SAS is marketed for critical server applications.