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Serial ATA supplants parallel ATA: industry

Serial ATA proponents come out swingin' with a host of gearrn



Storage connection woes have prompted many players to get behind serial ATA in a big way.

The technology — which has reached specification level 1.0 with product rollout underway; level II product releases are expected in 2004 — is designed to replace the parallel ATA physical storage interface,

says Knut Grimsrud, chair of the serial ATA steering committee, and Intel’s principal engineer on the serial ATA specification.

Essentially, the technology affects a variety of segments including desktop, mobile and consumer electronics, as well as servers and networked storage.

Serial ATA can be used to connect internal storage devices like hard disks, DVDs and CD-RWs to the motherboard in desktop and mobile PCs, servers and networked storage.

“”The reason we’re doing serial ATA in the first place is to address several shortcomings in parallel ATA,”” says Grimsrud.

“”Chief among them is the ability to efficiently integrate the controller into both chipsets and disk drives. Parallel ATA has a lot of pins on it, and it also uses high voltage signalling, which is difficult for chip designers and disk drive designers to continue to efficiently integrate.””

As such, Grimsrud says the primary benefits of serial ATA include ease of use, higher performance and design flexibility. “”Serial ATA is very pin-efficient — it only has four signal lines instead of the big ribbon cable connector that is usually associated with parallel ATA — and it also uses very low voltage signalling, so it’s very conducive for efficient integration in the modern manufacturing process.””

On the performance front, he says level 1.0 starts at 1.5 Gigabits, which gives an effective user data rate of 150Mbps. Level II is expected to have a signalling speed of 3 Gigabits, he adds.

“”It was engineered from the start to be able to accommodate several speed doublings in terms of interface rate — it was not clear that parallel ATA had the head room to support several more speed doublings. In fact, you can see historically that the performance trend for parallel ATA looks like it was tapering off.””

Players get into the game

Already industry players such as Seagate and Maxtor are touting the benefits of serial ATA.

At the recent Storage Networking World in Scottsdale, Ariz., Intel said it plans to develop, in concert with Emulex Corp., storage processors that for the first time integrate Serial ATA, Serial Attached SCSI (SAS) and Fibre Channel interfaces within a single architecture.

Grimsrud says the joint development will deliver enhanced performance and integration across the three most widely used storage system interfaces.

Meanwhile, others are on the product rollout bandwagon. Josef Rabinovitz, president and CEO of JMR Electronics, says JMR is about to launch its PSAN storage application, which delivers network storage functionality at 270MB/sec sustained throughput using serial ATA. The gear will be available to Canadian resellers through EMJ and Bell Micro.

“”With serial ATA, it’s a lot easier to be connected,”” Rabinovitz says.

“”With parallel ATA, you had a 40-pin ribbon cable (into a computer motherboard or controller) and it took a lot of space and blocked a lot of airflow inside the computer; whereas the cabling is very narrow with serial ATA and doesn’t block any airflow . . . And you get faster speed out of serial ATA as the bus goes through.””

The connector using serial ATA is also designed for hot swap, whereas parallel ATA is not, he says, highlighting another benefit of the technology in terms of removability for the drive. Grimsrud agrees, saying parallel ATA is very difficult to add new capabilities “”because there’s so much legacy built into it; for example, the connector style is not conducive to hot plugging.”” Conversely, with serial ATA you can upgrade your system on the fly (enable new usage models where you can plug in a storage device on the fly), which gives new features and benefits to users.

Rabinovitz says while other technologies have tried to transition to a serial bus in the past, serial ATA will win out because of the power in numbers. “”There’s such a high level of vendors pushing for it — and they are so strong into the market — that there’s no reason why the market would go in a different direction . . . All vendors from drive, controllers to motherboard providers are inside the serial ATA group, trying to go into the technology.””

Grimsrud says previous efforts include 1394. “”While this is a successful interface, it’s not a high volume storage connection. Originally 1394 was envisioned as the disk drive connection and that hasn’t really happened.”” The reason 1394 is not a popular disk interface is because it’s not software compatible (like serial ATA).

VAR Vision

For resellers, opportunities come in a myriad of ways. “”It’s an easy to use technology from a plug and play situation,”” says Rabinovitz. “”It’s an opportunity to have some removable drive available inside the computer itself, and outside in the storage. And it’s a better performance, eventually, for the bus structure than parallel ATA.””

As such, Grimsrud says resellers can benefit in terms of having easier user upgrades. “”The benefits … of features (and) probably installation ease.””