Adaptec 51645 Installation And User Manual

Also see for 51645: Quick start guide Quick start guide Installation and user guide Installation and user guide Installation and user guide

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Adaptec 51645 Installation And User Manual Manual pdf 73 page image

Appendix A: Introduction to SAS ● 73How is SAS Different from Parallel SCSI?In summary, although SAS and parallel SCSI both use the SCSI command set, how they movedata from one place to another is very different. To support point-to-point serial datatransport, SAS introduces new types of connectors, cables, connection options, andterminology.Generally speaking, SAS is faster and more flexible than parallel SCSI, and provides moreoptions 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 Serial Attached SCSIParallel interface Serial interfaceMaximum speed 320 MB/sec shared by alldevices on the busMaximum speed 300 MB/sec per phy when in half-duplex modeSupports SCSI devices only Supports SATA and SAS disk drives simultaneouslyUp to 16 devices per SCSI channel More than 100 disk drives per SAS card, using anexpander (see page 72) or 50 SATAII disk drives.Supports single-port devices only Supports single- and dual-port devicesUses SCSI IDs to differentiate betweendevices connected to the same adapterUses unique SAS addresses to differentiatebetween devicesUser intervention required to set SCSI IDs SAS addresses self-configured by SAS devicesRequires bus termination Requires no bus terminationStandard SCSI connectors SAS connectors (see page 32)