RDMA for Advanced Networking

Arthur Cole

Now that high-bandwidth connectivity solutions like 10 GbE and Infiniband are competing for attention in the enterprise, although not necessarily against each other, the benefits of RDMA (remote direct access memory) are starting to be felt.


RDMA has been around for a while, but has largely worked behind the scenes as a means to shuttle data from place to place without gumming up whatever operating systems are in play. Low-cost storage enthusiasts are particularly jazzed about iSCSI Extensions for RDMA (iSER), which is being touted as the protocol of choice for pushing both 10 GbE and Infiniband solutions to the edge.


iSER for Infiniband got a shot in the arm last month when IDC pinned it as one of the enabling technologies that will push Infiniband into the multimillion dollar range by the next decade. It's worth noting that Infiniband supports both iSER and SCSI RDMA to connect block storage devices to servers.


Networking firm Voltaire has been a proponent of RDMA for Infiniband several years now, helping to launch the extension in 2005 by opening up its protocol sources to Linux users. More recently, the company has signed on with HP and Intel to merge the RDMA-friendly Grid Director switches with Xeon-based ProLiant c-Class Blades. A separate deal with Novell pairs the Grid Backbone Infiniband switch with the SuSE Linux Enterprise Real Time platform.


RDMA and Ethernet have a lengthy history together as well, but the development of faster services like 10 GbE has opened the door to new possibilities. At this week's HP Technology Forum, Chief Technologist Hal Woods talked up the combination of iSER and 10 GbE as a means to propel iSCSI into the upper echelons of storage by dumping such pesky operations as TCP/IP offload.


The RDMA/10 GbE combination is already starting to show up in hardware, too. Witness Broadcom's newest NetXtreme network interface controller that pulls iSCSI block storage, RDMA and 10-gig Ethernet onto a single-chip device.


More and more, it looks like even average-sized enterprises will have to contend with a mixed bag of Ethernet, Infiniband and even Fibre Channel connectivity. With the goal being a unified data infrastructure, at least there are underlying technologies that are at home in any environment.

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