SATA: Evolutionary or Revolutionary Disk Technology?

Wednesday Mar 19th 2003 by Leslie Wood
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SATA: Evolutionary or Revolutionary Disk Technology?

Serial ATA (SATA) is a glossy new storage technology designed with the intent to eventually supplant parallel ATA (PATA). According to some industry experts, SATA storage solutions could cut the price of high capacity, server-attached storage by as much as 60 percent. But, if that's really the case, what's keeping SATA from taking the storage market by storm?

The Adoption of a New Technology Takes Time

According to Knut Grimsrud, Intel's technology initiative manager, as with any technology, it not only takes time to move from first products in the market to broad market availability, it also takes time to educate mainstream consumers about the benefits, and it takes time to get IT managers to qualify the new products.

Joni Clark, Seagate's Serial ATA project manager, says SATA has been embraced by the entire industry like no new industry standard before it. "The adoption rate for SATA is expected to reflect the usual requirements of the market, because as chip makers, controller and motherboard vendors, and hard drive manufacturers release various products, those markets that can best take advantage of SATA's new features first will most likely be the early adopters." In addition, Clark believes that as higher volumes enable cost parity with parallel PATA products, adoption will ramp up more quickly and SATA will ultimately replace PATA in all areas where PATA now plays a leading role.

SATA: Improving Integration Efficiency

A primary motivation behind developing SATA was to improve integration efficiency. This is accomplished, according to Grimsrud, by reducing the pincount necessary to support the interface as well as by reducing the signaling voltages to better accommodate the latest manufacturing processes. "These characteristics make SATA inherently more efficient to integrate than PATA, and it is expected to translate into a long-term cost advantage over PATA," claims Grimsrud.

Tracy Yang, LSI Logic's manager of its RAID Storage Adapter, says the SATA standard is aimed at resolving the key shortcomings of the PATA interface while retaining a cost advantage due to the following characteristics:

  • Point-to-point connection for higher performance -- 150MB/sec per drive
  • Thinner and longer (1m vs. 18 inches) for easy routing
  • Hot-swap capability, first party DMA, and enhanced reliability with the addition of 32-bit CRC error correction
  • Better connection design for easy installation and better device reliability
  • Connector size that allows 2.5" FF drives
  • No 5 volts legacy, allowing for the deployment of new silicon technologies

SATA II and Cost Reductions

Hardware based on the Serial ATA II specification is expected to appear by 2004. SATA II will be compatible with SATA 1.0, but it will feature some SCSI-like qualities that SATA presently lacks. If hard drive manufacturers match SATA II with some server-rated devices, inexpensive drive technology could possibly drive down the acquisition cost of low to mid-range servers, which will definitely have an effect on the storage industry as a whole. "The present day economic situation will challenge vendors to respond in a variety of ways; however, the SATA Working Group will continue to define technology that meets customer's demands," Grimsrud says.

Yang says that even though PATA rules the majority of the low-end servers and workstations market and SCSI has the majority of the enterprise server market, the future generation of SATA II products will create a market share shift from SCSI to SATA. "With improvement of reliability and availability, the SATA II product is poised to penetrate into some enterprise storage systems, but it will be a task for hard drive manufacturers to match enterprise-level features (speed, reliability, mechanicals) with the low price that has typically been identified with the IDE/SATA market."

Page 2: Will SATA Overtake the SCSI Market?


Will SATA Overtake the SCSI Market?

On specifications, SATA is closing in on SCSI and in some respects may even eventually overtake it, but is SATA ready right now? Clark says that SATA is not designed to, nor is it expected to, surpass the specific capabilities of the SCSI interface. "SCSI offers a much richer command set than SATA 1.0 or SATA II," states Clark. She also says that because SCSI has a myriad of built-in features and protocols, it is easier to customize to a specific application, giving customers the freedom that they have become accustomed to.

However, she does say that SATA is indeed meant to replace PATA. "SATA unleashes the power of ATA, but to keep the cost within the expectations of PC and entry-level system builders, SATA storage must be designed around the appropriate workload." Clark also contends SATA is designed for PCs and those cost sensitive servers that handle the lower transactional workloads.

According to Yang, SATA addresses the market's needs and requirements for cost/performance with powerful industry forces driving its development. In addition, she says with all the major manufacturers announcing SATA drives during Q4 2002 and Q1 2003, the ATA revolution is coming on strong. "SATA will co-exist in the PC market with PATA at the beginning, then eventually replace it." SATA chipset integration, she continues, is scheduled for release by the second half of 2003, and the forthcoming SATA II technology is the one foreseen to really close the gap with most SCSI applications.

According to the SATA Working Group, SATA defines a roadmap that starts at 1.5 gigabits per second (equivalent to a data rate of 150MB/s) and migrates to 3.0 gigabits per second (roughly 300 MB/s), then to 6.0 gigabits per second (600 MB/s) -- six times faster than the current ATA standard -- and allows for more flexible and intelligent systems. This roadmap supports up to 10 years of storage evolution, based on historical trends.

Impacting Storage Budgets

Right now, everyone in the IT industry is watching SATA technology, so what type of impact will it have on companies' storage budgets in 2004? Clark says that part of the beauty of Serial ATA is that its adoption has been made as simple as possible -- making the market transition almost seamless.

"Certainly, the entire market will begin the transition to SATA this year, but the impact on budgets may well be incremental, just as it would be if the transition were to a PATA interface," says Clark.

Yang says that LSI Logic is already starting to see its customers move from the PATA interface to the SATA interface. "SCSI and Fibre Channel will continue to be the choices for the high-end server markets, but with SATA II features, SATA will start penetrating to the high-end server markets, especially in the cost sensitive and near-line storage areas," she concludes.


» See All Articles by Columnist Leslie Wood


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