SCSI, ATA Groups Build Serial Compatibility

The SCSI Trade Association and the Serial ATA Working Group team up on serial port spec.

Hard drives and direct-attached storage cabling are notoriously tedious to install, but two industry groups are now working together to simplify that.

Next year, the SCSI Trade Association—which evolved from an earlier working group developing the serial-attached Small Computer System Interface—and the Serial ATA Working Group, which works on the replacement for the older parallel Advanced Technology Architecture, hope to complete a serial port specification that is compatible with both technologies, said LSI Logic Corp.s Harry Mason, president of the SCSI group.

"When we created the vision for serial-attached SCSI, we wanted to leverage the physical work that had gone on in the Serial ATA group. Philosophically there was some agreement, but there were some legal and technical issues about the ability to share information," he said, at the Server I/O conference this week in Monterey, Calif.

Both groups are marketing organizations with technical subgroups, and neither is an official standards body, said Mason and Serial ATA board member Susan Bobholz. But both have common members and influence with T10 and T13, which are the SCSI and ATA units of ANSIs International Committee on Information Technology Standards.

Once the serial specifications for SCSI and ATA are ensured to be fully compatible, the newly allied group will consider new features to help bring the simpler and less expensive ATA up to SCSIs level of reliability. For example, SCSI today runs at 3G-bps, but ATA runs at just 1.5G-bps. Both could have 6G-bps connections by 2007, Mason and Bobholz said.

Also, ATA only has point-to-point connections, whereas SCSI has multi-initiators with error management. In another example, parallel ATA today has expanders for one-to-many ports, but the serial version doesnt, despite its allotment in the specification. Buffering, queuing, and multiplexing all need work for serial fabric and edge expanders to be on the market in 2004 and 2005, they said.