Adaptec 3405 User Guide - Page 81

Appendix A: Introduction to SAS ● 81 How is SAS Different from Parallel SCSI? In summary, although SAS and parallel SCSI both use the SCSI command set, how they move data from one place to another is very different. To support point-to-point serial data transport, SAS introduces new types of connectors, cables, connection options, and terminology. Generally speaking, SAS is faster and more flexible than parallel SCSI, and provides more options for building your storage space. SAS lets you mix SAS and SATA disk drives together, and lets you connect many, many more devices. This table describes many of the main differences between the two interfaces. Parallel SCSI Parallel interface Maximum speed 320 MB/sec shared by all devices on the bus Supports SCSI devices only Up to 16 devices per SCSI channel Supports single-port devices only Uses SCSI IDs to differentiate between devices connected to the same adapter User intervention required to set SCSI IDs Requires bus termination Standard SCSI connectors Serial Attached SCSI Serial interface Maximum speed 300 MB/sec per phy when in halfduplex mode Supports SATA and SAS disk drives simultaneously More than 100 disk drives per SAS card, using an expander (see page 80) or 50 SATAII disk drives. Supports single- and dual-port devices Uses unique SAS addresses to differentiate between devices SAS addresses self-configured by SAS devices Requires no bus termination SAS connectors (see page 40)