How Is Sas Different From Parallel Scsi - Adaptec ASR-6805Q 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
Proprietary and Confidential to PMC-Sierra, Inc.
Document No.: CDP-00277-02-A Rev. A, Issue:
Serial Attached SCSI RAID Controllers Installation and User's Guide
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 SAS Expander Connections
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 Cables on page 31)
on page 72) or 50 SATAII
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