How Is Sas Different From Parallel Scsi - Adaptec RAID 3085 Installation And User Manual

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
Appendix A: Introduction to Serial Attached SCSI
Serial Attached SCSI
Serial interface
Maximum speed 300 MB/sec per phy when in half-
duplex mode
Supports SATA and SAS disk drives simultaneously
More than 100 disk drives per SAS card, using an
expander (see page
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
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