Serial Attached SCSI technologies and architectures, 4th edition

devices. The SAS-2 receptacles are universal because they do not have table routing or subtractive

routing restrictions.

Figure 17: Cable connector key slot positions

SAS-2.1 adds Mini SAS 8x internal and external connectors. The Mini SAS 8i HD (internal) connector

is a hybrid that combines two serial, general-purpose input/output (SGPIO) buses. The Mini SAS 8x

HD (external) connectors support both passive and active cables.

SAS drive performance

HP uses the latest SAS technologies to build highly scalable and reliable storage solutions. In

enterprise server environments, SFF SAS drives excel in performance and reliability. The smaller

platters of SFF SAS drives inherently have lower seek times than 3.5-inch large form factor (LFF) SAS

drives. That is an important advantage in file servers with frequent random accesses.

At the same time, SFF drives support higher drive densities per U without a significant increase in

power consumption. SFF drives require only 70 percent of the space and 50 percent of the power of

LFF SAS drives. Higher drive densities give you better overall performance, greater reliability, and

lower operating costs.

For more information on SAS drive performance, refer to the HP technology brief ―Performance

factors for HP ProLiant Serial Attached SCSI‖ at

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01460725/c01460725.pdf.

Conclusion

SAS technologies, including differential signaling and active cables, continue to evolve and improve.

Dual-domain and dual-path configurations can provide effective solutions if you are looking for a

higher level of redundancy, reliability, and increased data availability within a storage network.

Storage network redundancy through dual-domain configurations can eliminate single points of failure

and make it possible to tolerate HBA failure, external cable failure, expander failure, and failure in a