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  Adaptec 29160 SCSI Card 
  Jul 20, 2001, 10:00am EDT 

Ultra160 Overview, Performance

By: Sander Sassen

As faster harddisks, Gigabit networking and other data-intensive applications, as well as the new 64-bit PCI interface, push the bandwidth envelope for high-performance workstations and servers, we need a solution that is both proven and capable of responding to new demands. Ultra160 SCSI, the new generation of the Small Computer System Interface (SCSI), takes performance to the next level, delivering twice the speed of Ultra2 Wide SCSI and four times that of earlier Ultra Wide technology.

For fifteen years, SCSI has been the I/O and storage solution of choice for computers ranging from the original Apple Macintosh to today's most advanced, mission-critical network servers. From its initial 5 MB/s throughput to today's 160 MB/s, SCSI has consistently offered the highest performance with the lowest CPU overhead.

Ultra160 SCSI is a natural progression in the continually evolving and improving SCSI technology. Ultra160 SCSI boosts the throughput of the Ultra2 Wide SCSI standard (80 MB/s) by sending two data bits per clock cycle instead of one, resulting in a maximum data transfer rate of 160 MB/s. This double-transition clocking allows both the data and clock lines to run at 40 MHz. Double transition clocking is only one of the many added features of Ultra160 SCSI that makes it such an improvement over the current designs.

High-end computer systems need increased data transfer capacity for their storage subsystems to keep up with the rapidly increasing data transfer rates harddisks are delivering. Due to higher track and platter densities and faster spindle speeds, we now see an annual 35% growth in the maximum harddisk throughput. To prevent the actual databus, SCSI in this case, but the same applies to UDMA/IDE, from being saturated, and to avoid limiting the number of drives that can be connected to the bus, the bus data transfer capacity needs to grow at a similar rate.

Consequently, bus data transfer capacity needs to double every two years to keep the available bandwidth at four times the maximum throughput of a single harddisk, partly to prevent the bus from saturating if more than one harddisk is connected. More importantly, other I/O also needs to be sent across the SCSI bus, as the SCSI bus is a command- rather than a data-bus.

Furthermore, faster network I/O, such as Gigabit networking, drives the demand for increased bus throughput. To support both inbound and outbound data with Gigabit networking, a storage subsystem may require a data transfer capacity of over 200 MB/s.

1. Introduction
2. Ultra160 Overview, Performance
3. Ultra160 Overview, Data Integrity
4. Ultra160 Overview, The SCSI vs. IDE Discussion
5. Adaptec SCSI Card 29160
6. Technical Support
7. Conclusion

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