IndustryWatch
Serial Attached SCSI Explodes into the Embedded Arena Now that there are fully integrated SAS products in the marketplace and costs are decreasing, SAS is rapidly growing in the embedded marketplace. The time has come for the embedded market to fully embrace the serialization of storage interface technologies.
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by Matthew Knowles, PhD,
tached SCSI (SAS) technology at the enterprise level and the recent availability of SAS at the mid and entry level is providing unprecedented performance and flexibility to infrastructure and storage solutions. As SAS is now ramping in the IT markets, the stability of the technology is maturing and the price point for SAS implementations is going down as it is driven by the large volume IT markets. mpanies providingIntel solutions andnow other member companies of the SCSI Trade Asploration into products, technologies companies. Whether goal is toblocks researchto theprovide latest sociation (STA)and now have the SASyour building all pplication Engineer, or jump to a company's technical page, the goal of Get Connected is to put you the of high-speed rvice you require for benefits whatever type of technology, serial communications to both IT and embedded markets. anies and products you are searching for. The speed and scalability of SAS brings realtime performance to large storage arrays or inter-box communications. This presents a new opportunity to enhance next-generation embedded system design with SAS technology to create scalable designs with improved performance and flexibility.
Why SAS?
Over the past 20 years, disk interface technology has followed two parallel paths in the IT desktop segment and the enterprise market segment. Personal computer desktops, commonly sold to consumers and businesses, have used parallel ATA (PATA) controllers and disk drives as the mass storage device of choice. The term PATA is inclusive of IDE and Ultra IDE, Get Connected which arewith also used tomentioned describe these controllers and disk drives. companies in this article. www.rtcmagazine.com/getconnected In the enterprise market, parallel SCSI has dominated for highperformance, high-reliability disk drives for everything from
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Get Connected with companies mentioned in this article. www.rtcmagazine.com/getconnected
n.
64
January 2007
Parallel SCSI Bandwidth Evolution 350
Megabytes per second
er exploration Intel ther your goal speak directly cal page, the The need for reliable, scalable, high-performance digital ght resource. storage is rapidly expanding in both the worlds of IT computtechnology, ing and embedded systems. In IT, the availability of Serial Ats and products
300 250 200 150 100 50 0
SCSI-1
Figure 1
SCSI-2
Ultra SCSI
Ultra2 SCSI
Wide Ultra2
Ultra 160
Ultra 320
Parallel SCSI Bandwidth Evolution.
small servers to mainframes and storage arrays. As the needs for higher-performance I/O increased over the past 20 years, parallel SCSI has maintained and executed to an aggressive roadmap of increased throughput graphically shown in Figure 1. Parallel SCSI has evolved from a 5 Mbyte/s standard to 320 Mbytes/s with Ultra320 SCSI. In the desktop arena, PATA has maintained a similar roadmap of performance (topping out at 133 Mbytes/s) while maintaining cost structures for the consumer and business PC market. Although both technologies were successful for their respective market segments (PATA achieving 133 Mbytes/s and SCSI hitting 320 Mbytes/s), both reached fundamental technical and logistical challenges due to the parallel nature of the interfaces. Parallel communications require a large number of conductors (40/80-pin for PATA, 68-pin for SCSI), which makes for bulky cabling and increased signal cross-talk with increasing frequencies. Both have jumper/termination requirements and support a limited number of devices (2 for PATA and 15 for SCSI). Neither can support hot-swap of hard drives required for serviceability of storage designs.