USB 3 chip will bring RAID to external drives

Symwave says its USB 3.0 chip can move 500MB of data in a second

Symwave, one of the first companies to design silicon for USB 3.0, is revealing more details about its SOC (system on a chip) using the high-speed standard at the Hot Chips conference on Monday.

USB 3.0, which debuted last November, is designed to provide throughput as high as 5GBps, up from just 480MBps for USB 2.0. Symwave says its USB 3.0 SOC can be used in external storage devices that ship data as fast as 500MBps.

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Symwave is trying to tackle the same problem plaguing many consumers and enterprises as they use more high-definition multimedia content and have to save more data in general. Demand for storage capacity continues to rise, and backing up that data from a laptop or desktop to an external drive can take hours. USB 2.0, nearly ubiquitous on PCs and portable consumer electronics today, can be a barrier.

"You're pretty much communicating through a straw," said Gideon Intrater, Symwave's vice president of solutions architecture. The SATA I/O protocol used with most hard drives can transport about 300MBps, while USB 2.0 typically delivers just 20MBps or 30MBps, he said. "USB 2 was good as long as you had 100GB on your hard drive, but now it's just way too slow."

By way of comparison, a 25GB high-definition movie would take 13.9 minutes to transport over USB 2.0 and just 70 seconds with the new standard, according to the USB Implementers Forum. The contents of a 1GB thumb drive could be transferred in 3.3 seconds, versus 33 seconds previously.

The SOC that Intrater will discuss on Monday will boost that performance up to and beyond the top speed of SATA. It's a chip for external storage devices that includes several key functions for either HDD (hard disk drive) or SSD (solid-state drive) units. The chip will allow OEMs of storage devices and enclosures to offer speeds as high as 500MBps because it includes support for RAID 0 configurations. Using RAID, the system maker can build an enclosure with two drives and either feed data faster by addressing both drives at once or feed the same data to both drives so that one is a mirror of the other, Intrater said.

RAID hasn't been a realistic option with USB 2.0 because just one SATA drive can easily saturate the USB connection, according to Intrater. In addition, USB 2.0 has been limited in the kinds of devices it can power by itself. USB 3.0 can carry as much as 900 milliamps, up from just 500 milliamps for USB 2.0, he said. That will make it easier to power a portable RAID array of two drives, as well as to power faster-spinning HDDs than before and to charge some smartphones and other devices that the older standard couldn't fill up, Intrater said.

USB 3.0 was also designed to put fewer demands on a system's CPU during backup operations, he said. Products that support the new standard will be backward compatible with USB 2.0, so if any component in a set of linked devices isn't made for the USB 3.0, the connection will fall back to the older standard.

In addition to supporting RAID and the protocol conversion from SATA to USB 3.0, the Symwave chip can perform authentication and encryption. It uses the recently approved IEEE 1667 standard for authentication, which Microsoft has said it will include in Windows 7. For encryption, Symwave is using the XTS-AES technology, based on the Advanced Encryption Standard. System makers can choose to implement it in 128-bit or 256-bit mode, Intrater said.

Symwave, a fabless semiconductor company based in Laguna Niguel, Calif., was founded in 2004 and restructured itself last year around the goal of designing chips for the emerging USB 3.0 standard. It faced some challenges, including the speed of the protocol itself. At the 5GHz speed of USB 3.0, bits of data travel so fast that on a 10-foot cable there can be multiple bits traveling over the wire at the same time, Intrater said.

Price is another issue. The final products will have to stay close to the price range of USB 2.0 gear, with only a small premium, Intrater said. Despite the huge performance advantage, vendors won't be able to charge twice as much, he said.

The company has made prototypes of the SOC and expects OEMs to ship products based on it by the end of this year.

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