HP 418800-B21 Redundancy in enterprise storage networks using dual domain SAS - Page 11

Appendix B: Enabling technology The advent of SAS and SATA drives makes the implementation of dual-domain SAS technology possible. Hardware and protocol commonality enables the redundancy and reliability of dual-domain SAS technology and reduces the number of possible single points of failure within a system. SAS and SATA technology Parallel storage technology has reached hard limitations with respect to volume and speed. The physical architectural differences found in SCSI and ATA drives also mean that there are limitations for connectivity. Serial technology has eliminated these connectivity barriers to connectivity (see Figure B-1). Serial attached SCSI and ATA are complementary technologies based on a universal interconnect, so SAS users can choose to deploy cost-effective SATA drives in a SAS storage environment. Requirements for physical connectivity have dropped from the 68 wires per cable required by parallel technology to 4 wires for serial. In addition to reducing the size of wiring and connectors, serial technology reduces the incidence of crosstalk, signal skew, and other forms of signal error found in parallel storage networks. Serial "star" topology, enabled by expanders, is more flexible, easier to manage, and common to both SAS and SATA drives. Figure B-1. Comparison of parallel and serial technologies Bandwidth Physical layer Topology 11