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Comparing EMC Symmetrix DMX-3 vs. Hitachi Data Systems USP1100


RapidIO steams into storage

RapidIO might sound like Europe's latest entry for high-speed rail transport, but rather than shuttling passengers about, RapidIO moves data faster and more efficiently than some existing interconnect technologies.

RapidIO is a packet-switched fabric design that had its genesis in work begun by Motorola in 1997. Motorola's efforts were bolstered by Mercury Computer when it released an initial specification in 1999, but the technology has since flown under the radar of most storage professionals. However, with new specifications recently released and more on the way--not to mention a growing membership in its supporting trade association that includes some notable storage companies like EMC and AMCC--that's likely to change.

Although not specifically designed for storage applications, RapidIO's high speed, low-latency capabilities and small packaging could replace some of the proprietary ASICs currently used in backplane and other internal storage implementations. "RapidIO is a full 10Gb serial fabric, and it gives you really low latency that's deterministic," says Tom Cox, executive director of the RapidIO Trade Association, which was formed in 2000. Because RapidIO includes full error correction and redundancy, "everything is very secure--that's one of the reasons it's popular on the storage side," he adds.

EMC, which is a founding member of the RapidIO Trade Association, hasn't yet incorporated the technology into any of its products and is "unable to disclose product futures," says Wayne Adams, senior director of industry standards at EMC's office of the CTO. Adams cautions storage users not to expect RapidIO to replace technologies like iSCSI over Ethernet or Fibre Channel, but adds that "the RapidIO community has targeted clustered storage systems as a potential application."

The potential of RapidIO is intriguing. Indeed, it's plausible that it could be used to interconnect storage controllers or even for host connectivity. With Ethernet or iSCSI, latency is different every time, while RapidIO is very consistent, allowing for greater speeds. "We can do what both Ethernet and other message-passing protocols can do," says Cox, "but it can also do the full RDMA load/store/read/write/modify memory operations that PCI, InfiniBand and others can do."

Storage vendors other than EMC and AMCC are apparently interested in the standard, although most of the activity is under the covers right now. "I can only say that I do know of design wins in storage OEMs," says Cox. He notes that because RapidIO will initially be incorporated into otherwise proprietary designs, it's unlikely vendors will divulge details about their specific efforts.

--Rich Castagna

Article 3 of 14
This was last published in January 2007

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