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SATA And SAS Hold Big Promise For Servers

Today, if you talk about server technology, you must also talk about storage.

"Analysts tell us that, in today's server deployments, 50 percent of the sale is server and the other half is storage," said Eric Herzog, vice president of ARIO Data Networks, San Jose, Calif. "It used to be 80 percent server and 20 percent storage. When thinking about servers, it's clear that the complete solution will heavily involve storage of some sort."

Fortunately, new serial-based technologies, such as the already released Serial ATA (SATA) and the upcoming Serial Attached Storage (SAS) technology, promise greater speeds, higher levels of reliability, and increased affordability and scalability—so that server manufacturers can deliver even more in terms of storage options.
"[The move to serial technology] is an important evolution in the arena of storage and servers over the next couple of years that will set a new standard going forward for storage products inside of servers," said Rich Palmer, group manager for External Storage Solutions at Hewlett Packard, Houston. "The serial market opportunity is driven by the need to optimize the performance of the storage platform inside the server. One of the main reasons to move to serial is to push the IO barrier. And, by moving to SATA, we've added in hot-plugability, and greater scalability and performance."
Last May, HP began shipping its ProLiant ML100 server, which uses SATA drives and is aimed at the small to medium sized business user.
Today, SATA drives provide 1.5 gigabits per second—equivalent to a data rate of 150MB/s. The specification's next generation, which was formally adopted in July, boosts speeds to 3.0 gigabits per second or 300 MB/s. "SATA is faster and more robust than parallel ATA for a better quality of service and higher performance, which are all benefits to the server side]," said Herzog.
SATA's interface specification, first released in August 2001, initially was intended for entry-level servers and network attached storage (NAS) applications, although the technology now is expected to penetrate higher end servers.
"Compared with the historical context of how fast some of these transitions have been occurring, the transition from parallel ARA to serial ATA has been amazingly smooth and quick, especially considering the size of the change," said Knut Grimsrud, senior principal engineer at Intel, and chairman of the board for the Serial ATA International Organization, an industry organization for the standard. "The next step for SATA IO is to continue to define features and compatibilities for SATA, and to create an infrastructure for compliance and interoperability. We've come so far, so quickly, that we need to make sure that the entire infrastructure is sound so that newcomers don't struggle."
SAS meanwhile, is a SCSI technology replacement that will evolve over the next six to 12 months. "Because SAS is built on the SCSI platform it has the inherent benefits of SCSI, including higher MTBF, reliability, robustness and performance, but adds the benefits of hot plugability and the improvement of performance and scalability," said Palmer. "SAS gives us the ability to drive IO into each of the drives, each of the components of the architecture, because it is a point-to-point architecture."
SAS, which was published as an official standard in November 2003, promises to increase hard drive performance to 3 gigabits per second (Gbps), compared with 2 Gbps offered by Fibre Channel drives. Although not currently available, vendors predict that SAS products will become a common sight in servers in mid to late 2005.

Hailey Lynne McKeefry of Professional Ink ( is a freelance writer based in Belmont, Calif.