How is SAS Different from Parallel SCSI?In summary, although SAS and parallel SCSI both use the SCSI command set, how they move data fromone place to another is very different. To support point-to-point serial data transport, SAS introducesnew types of connectors, cables, connection options, and terminology.Generally speaking, SAS is faster and more flexible than parallel SCSI, and provides more options forbuilding your storage space. SAS lets you mix SAS and SATA disk drives together, and lets you connectmany, many more devices.This table describes many of the main differences between the two interfaces.Serial Attached SCSIParallel SCSISerial interfaceParallel interfaceMaximum speed 300 MB/sec per phy when in half-duplexmodeMaximum speed 320 MB/sec shared by all deviceson the busSupports SATA and SAS disk drives simultaneouslySupports SCSI devices onlyMore than 100 disk drives per SAS card, using an expander(see SAS Expander Connections on page 62) or 50 SATAIIdisk drives.Up to 16 devices per SCSI channelSupports single- and dual-port devicesSupports single-port devices onlyUses unique SAS addresses to differentiate between devicesUses SCSI IDs to differentiate between devicesconnected to the same adapterSAS addresses self-configured by SAS devicesUser intervention required to set SCSI IDsRequires no bus terminationRequires bus terminationSAS connectors (see Cables on page 23)Standard SCSI connectors63Proprietary and Confidential to PMC-Sierra, Inc.Document No.: CDP-00277-01-A Rev. A, Issue:Serial Attached SCSI RAID Controllers Installation and User's Guide
