Seagate ST3300657SS Enterprise-Optimized 6Gb/s SAS Rivals Fibre Channel Perfor - Page 4

Enterprise-Optimized 6Gb/s SAS Rivals Fibre Channel Performance and Scalability at Lower Cost Expander Self-Discovery compelling performance/dollar value proposition Expander self-discovery simplifies administration than costly solid state drives (SSDs). while doubling storage scalability. Under the SAS-1 standard, connecting devices to the expanders was a host-based process. As long as the number of SAS drives in the storage pool was relatively small, this discovery scheme was reasonably efficient. But in network storage environments, where massive numbers of drives are typically employed, host-based discovery resulted in increased SAS messaging traffic between hosts and expanders and more time was needed to initialize systems. The SAS-2 standard resolves this issue by shifting the SAS discovery process from the host to the expander. Enabling 6Gb/s SAS expanders to perform device discovery themselves, automatically and in parallel, makes provisioning large systems of SAS drives both faster and easier to manage. This expander self-discovery technology plays a pivotal role in ensuring seamless scalability as network storage needs 10-Meter Maximum Cable Length A 10-meter maximum cable length extends connectivity by 66 percent supporting networked storage expansion beyond a single rack. 6Gb/s SAS delivers a remarkable 100 percent boost in transfer rate while also enabling the use of longer connecting cables (up to 10 meters, an increase from the 6-meter cables supported by 3Gb/s SAS). Achieving this improvement in throughput and maximum cable length required the use of decision deedback equalization (DFE) technology. DFE counteracts the signal attenuation effects that arise from greater cable lengths by deemphasizing lower frequency components at the transmitter and selectively boosting higher frequency components on the receiving end. This enables the use of 10-meter cables with no loss of signal integrity, while still maintaining compatibility with existing 6-meter cables. (and storage device quantities) inevitably grow. This 66 percent increase in maximum cable length 6Gb/s SAS: Optimized for the Enterprise pays significant dividends in the data center, enabling far greater flexibility in terms of wide- While the impressive capabilities of 6Gb/s SAS scale storage system deployment and installation. in network storage environments clearly derived This cable extension provides the flexibility to from the inclusion of standardized expander expand your network-attached storage beyond zoning and expander self-discovery technologies, the limits of a single rack using a 10-meter cable they are not the only aspects of the SAS-2 while ensuring the integrity of the data. standard that make 6Gb/s SAS so effective in enterprise storage arrays. Indeed, 6Gb/s SAS Spread Spectrum Clocking incorporates a variety of enterprise-centric features, including: 6Gb/s SAS doubles the data frequency of 3Gb/s SAS; this may result in a loss of cabinet shielding 6-Gb/s Transfer Rate efficiency due to the shorter wavelengths of the signals. The 6-Gb/s transfer rate enables rock solid enterprise-class performance at 2x the throughput of today's SAS or SATA environments. Higher throughput is always a desirable feature in any storage solution, but it's particularly important in enterprise data centers, where drives can be repeatedly accessed by multiple initiators. With double the transfer rate of its 3Gb/s SAS To combat this change in frequency, 6Gb/s SAS employs spread spectrum clocking (SSC), a slow-frequency (30-33 Khz) modulation of the data frequency. By reducing the peak values and spreading the radiated emissions over a broader range of frequencies, SSC helps to reduce EMIrelated issues. predecessor, 6Gb/s SAS delivers the speed necessary to keep up with the demands of hightraffic network storage environments. Delivering performance that's competitive and significantly less expensive than FC storage solutions, 6Gb/s SAS also offers a more Simplified Connectivity Simplified connectivity standardizes mini SAS connectors for cost-effective SAS solutions. To simplify cabling options and streamline integration, 6Gb/s SAS eliminates the expensive InfiniBand-style (SFF-8470, Figure 3) connector 4