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Serial Attached SCSI (SAS) is a new generation serial communication protocol for direct attached devices designed to allow for much higher speed data transfers and is compatible with SATA. SAS uses serial communication instead of the parallel method found in traditional SCSI devices but still uses SCSI commands for interacting with SAS devices.

SAS supports up to 16,384 addressable devices per port and point to point data transfer speeds up to 3 Gbit/s, but is expected to reach 10 Gbit/s by the year 2010. The SAS connector is much smaller than traditional parallel SCSI connectors allowing for small 2.5 inch drives.

The physical SAS connector is available in 3 different variants:

SFF 8482 - which is form factor compatible with SATA

SFF 8484 - hi-density internal connector for connecting up to 4 devices

SFF 8470 - hi-density external connector (aka Infiniband connector) for connecting up to 4 devices

Form factor compatibility with SATA allows for much cheaper SATA drives to connect to a SAS backplane. SAS drives are not compatible on a SATA bus and have their physical connector keyed to prevent any plugging into a SATA backplane.

Serial Attached SCSI supports three transport protocols:

Serial SCSI Protocol (SSP) — Supporting SAS disk drives
Serial ATA Tunneling Protocol (STP) — Supporting SATA disks behind an SAS expander
Serial Management Protocol (SMP) — for managing SAS Expanders

A SAS domain consists of a Host, Delivery Sub-System and End device. Each SAS device is assigned a World Wide Name (aka SAS address) assigned by IEEE for the particular vendor. The WWN uniquely identifies the device in a SAS domain just as a SCSI Id identifies a device in a parallel SCSI bus.

References

SAS General Overview

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	'''Serial Attached SCSI''' (SAS) is a new generation serial communication protocol for direct attached devices designed to allow for much higher speed data transfers and is compatible with SATA. SAS uses [[Serial communications\|serial communication]] instead of the [[Parallel port\|parallel]] method found in traditional [[SCSI]] devices but still uses SCSI commands for interacting with SAS devices.		'''Serial Attached SCSI''' (SAS) is a new generation serial communication protocol for direct attached devices designed to allow for much higher speed data transfers and is compatible with [[SATA]]. SAS uses [[Serial communications\|serial communication]] instead of the [[Parallel port\|parallel]] method found in traditional [[SCSI]] devices but still uses SCSI commands for interacting with SAS devices.

	SAS supports up to 16,384 addressable devices per port and point to point data transfer speeds up to 3 [[Gbit/s]], but is expected to reach 10 [[Gbit/s]] by the year [[2010]]. The SAS connector is much smaller than traditional parallel SCSI connectors allowing for small 2.5 inch drives.		SAS supports up to 16,384 addressable devices per port and point to point data transfer speeds up to 3 [[Gbit/s]], but is expected to reach 10 [[Gbit/s]] by the year [[2010]]. The SAS connector is much smaller than traditional parallel SCSI connectors allowing for small 2.5 inch drives.