STA Begins Planning Ultra 4 and 5 SCSI Specs

The SCSI Trade Association (STA, <A HREF="http://www.scsita.org/">www.scsita.org</A>) has laid out a roadmap to increase SCSI transfer rates four-fold. The latest Ultra 3 SCSI runs at 160 MBps, but the new plans will double that rate within the next two years -- which will be Ultra 4 -- and push the rate to 640 MBps by 2003 -- to be named Ultra 5.

The SCSI Trade Association (STA, www.scsita.org) has laid out a roadmap to increase SCSI transfer rates four-fold. The latest Ultra 3 SCSI runs at 160 MBps, but the new plans will double that rate within the next two years -- which will be Ultra 4 -- and push the rate to 640 MBps by 2003 -- to be named Ultra 5.

"We're not formalizing the features and functionality in Ultra 4 and Ultra 5 SCSI, but we believe the technology is meetable," says STA president Harry Mason.

Several industry trends are supporting the need to enhance SCSI capabilities. Higher processor and memory speeds demand higher data transfer rates from mass storage devices, requiring SCSI to continue to increase its performance. For example, Gigabit Ethernet can require data transfer rates up to 200 MBps. Enhancements to the PCI bus to increase bus width to 64 bits and speed to 66 MHz, along with alternatives to the PCI bus, also will require increasing data movement.

Mason says there is a Moore's Law in the performance industry that data transfer rates double every 2.2 years. "Whether we can follow that curve remains to be seen, but we need to be aware of it and support it," Mason says. Further driving the SCSI performance evolution is the exponential increase in data storage requirements for servers, a result of the widespread use of the Internet and of corporate databases, which often incorporate multiple data types such as text, graphics, audio and video.

Last September, the association approved features for the Ultra 160/m SCSI, based on the Ultra 3 interface. The "m" is for manageability, and it's the manageability features that are being implemented to improve speed. These features include Cyclic Redundancy Code (CRC) and domain validation. CRC protects data from being lost in the event of a poor connection during hot-plugging of a new drive into a system. Domain validation provides a new method for ensuring compatibility and that data transfers happen at the highest possible rate. If this rate is not possible, the device can shift to a lower speed before data transfer begins. This flexibility allows SCSI to tune its performance to the highest level the system will support.

Member companies also are developing manageability software to track errors and define how to make system adjustments to ensure maximum overall performance. New SCSI applications and configurations include static and dynamic switches, which allow multiple systems to be connected to multiple drive arrays. There are also expanders, hubs and bridges, which allow SCSI to be used for longer distances and reduce loading problems.

Market analysis firm Dataquest (www.dataquest.com) expects Windows NT server shipments to grow 23 percent and Wintel workstations shipments growing 36 percent this year, and the STA expects the use of SCSI to grow as well, especially since Windows NT has SCSI support built in. Mason says independent of incorporation with operating systems, SCSI has obtained a robust position in the server space and that more users will gravitate to SCSI because of its out-of-the-box usability.

Mason also says SCSI’s position in the enterprise will continue to grow as Fibre Channel hasn't garnered the market share that some predicted. In fact, Mason says, the more that data centers purchase storage boxes with Fibre Channel in the machine, the more they rely on SCSI to connect those machines. Not only that, but Mason says Ultra 160/m SCSI runs faster than Fibre Channel in certain implementations.

Suresh Panikar, director of product marketing for Mylex Corp. (www.mylex.com), a RAID controller vendor, says the development for faster I/O on SCSI has been amazingly fast. "[Progression] used to take five to 10 years. Now it's 18 months to three years," Panikar says.