SCSI Trade Association Releases Next-Generation SCSI Specification

The hype surrounding Fibre Channel seems to suggest that the SCSI interface will be relegated to the annals of history. However, the SCSI vendor community and the SCSI Trade Association (STA, San Francisco, <A HREF="http://www.scsita.org/">www.scsita.org</A>) say, &quot;not yet,&quot; and as proof, unveiled a next-generation SCSI interface specification based on Ultra3 SCSI, called Ultra160/m SCSI.

The hype surrounding Fibre Channel seems to suggest that the SCSI interface will be relegated to the annals of history. However, the SCSI vendor community and the SCSI Trade Association (STA, San Francisco, www.scsita.org) say, "not yet," and as proof, unveiled a next-generation SCSI interface specification based on Ultra3 SCSI, called Ultra160/m SCSI.

Systems based on the new interface are expected to become available sometime in the middle of next year. Like Ultra3 SCSI, Ultra160/m -- the m stands for manageability -- will be fully compatible with Ultra2 SCSI. This backward compatibility is expected to speed the adoption of the new interface by both OEMs and end users.

"The Ultra3 SCSI standard is kind of a smorgasbord of features, and vendors can take any of those features and still be Ultra3 compliant," says Sam Sawyer, enterprise product manager, Fujitsu America Inc. (San Jose, Calif., www.fujitsu.com). Those features include double-edge clocking, cyclic redundancy check (CRC), domain validation, packetization, and quick arbitration and select (QAS).

The Ultra160/m specification calls for inclusion of three major Ultra3 SCSI technologies: double-edge clocking, CRC and domain validation. Double-edge clocking allows systems to run faster by doubling the amount of data transfer without increasing clock frequencies. CRC provides extra data protection for marginal cable plants and external devices, ensuring integrity of transferred data. Finally, domain validation tests the storage network to get the right traffic speed.

Sawyer says packetization and QAS features aren't expected to be available for another 2 or 3 years.

Analysts expect Ultra160/m SCSI to extend parallel SCSI technology for use with Windows NT and Unix system workstations, video and Web servers and storage-area networks. International Data Corp. (Framingham, Mass.) predicts that parallel SCSI will represent more than 80 percent of the high-end disk drive market in 1999.

The Ultra 160/m boasts a doubling of the Ultra2 SCSI data transfer rate, and products incorporating Ultra160/m can test and manage a storage network so that the maximum reliable data transfer rate is used. If reliability is believed to be at risk, the bus will be slowed to a rate that is considered to be reliable. This "host adapter intelligence" is expected to provide more system autonomy and less IT manager involvement.

At 160 MBps, the new SCSI specification can offer performance levels equal to Fibre Channel, points out Harry Mason of the STA. "There's a lot of things to consider about incumbent interfaces," says Mason. "You don't need to use Fibre Channel for aggregating processor performance."

Mason doesn't expect use of SCSI to peak until 2005. "The adoption barriers [for SCSI] are smaller, and return on investment is faster and that's what it comes down to," he says. "We're [STA] not bashing Fibre Channel, but we have a market to attend to and we have SCSI users that want updates."

Other supporting vendors of the new interface include Adaptec (Milpitas, Calif., www.adaptec.com), Hewlett-Packard Co., LSI Logic Corp. (Milpitas, Calif., www.lsilogic.com), Mylex Corp. (Fremont, Calif., www.mylex.com), QLogic Corp. (Costa Mesa, Calif., www.qlc.com) and Quantum Corp. (Milpitas, Calif., www.quantum.com).