By Deni Connor
Network World, 09/24/01

As Gigabit Ethernet's popularity grows, users are pushing TCP/IP data across their networks ever faster. But servers are choking on the load.

In data transfers, the system CPU acts as a manager of applications running on the server and a traffic cop for data transfers between the disk drive and requesting devices. The CPU must repeatedly interrupt application processing and reach into memory to get disk data. So each bit of I/O the CPU processes slows down application processing. As a company aggregates multigigabit links, even a server CPU running at 1GHz or higher has little chance of keeping up with demands for data.

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Enter TCP Offload Engines, or TOE for short. TOE technology aims to take the server CPU out of I/O processing by shifting TCP/IP processing tasks to the network adapter or storage device. This leaves the CPU free to run its applications, so users get their data faster.

"TCP/IP processing can boost CPU utilization by as much as 50%," says Costa Sazunptzakis, a designer at Cisco, one of the companies involved in finding a fix for overloaded CPUs.

TOE

The idea of off-loading TCP/IP processing from the system CPU to specialized hardware is not new for server network adapters or mainframe environments, but it is for storage devices and controllers.

And the need for TOE has become especially acute with the advent of iSCSI, a pending standard that proposes the transport of block-oriented storage data over Gigabit Ethernet networks. Vendors supporting iSCSI include Cisco, with its SN5420 storage router, and Nishan, with the IPS 3000 Series IP Storage Switch.

"Implementing TCP off-load in hardware is absolutely a requirement for [iSCSI] to become mainstream," says Steve Duplessie, an analyst with the Enterprise Storage Group research firm in Milford, Mass. "TCP is required to guarantee sequence and deal with faults, two things block-oriented storage absolutely requires. Running TCP on the server will cripple the server eventually - so bringing the function into hardware is a must."

Arun Taneja, another Enterprise Storage Group analyst, agrees. "If storage vendors' products are able reduce the amount of CPU processing by 50%, that's a huge advantage, considering the processing will be done thousands of times," he says.

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Products soon to ship

Duplessie sees lots of activity and investment in this area and expects to see products this year.

IP storage

Companies including Adaptec, Emulex, Pirus and Surgient are at work on various types of storage products, from controllers to switches, that support TOE (see graphic). And Trebia Networks, a start-up in Acton, Mass., is hoping to supply the silicon that will let these controllers work.

SANs

"Storage networks run at one gigabit, so any device that is processing packets needs to run at that speed," says Brendan Howe, director of marketing for Trebia Networks. "In software processing, some processing cycles of the CPU will still be consumed while the server is busy doing application services processing. In hardware, you can achieve line speed for interfaces and not consume CPU processing cycles."

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Questions to ask TOE vendors Does your device merely accelerate TCP/IP processing or off-load it entirely? Does it off-load the entire TCP/IP stack or just part of it? Is acceleration performed in hardware or software? By how much does your off-load facility improve performance?

Chris Baldwin, a venture capitalist with Charles River Ventures in Boston, has put money into several storage companies that are working on TOE, including Pirus and Storigen, which was still in stealth mode at press time.

"Networking speeds have outpaced processor speeds with respect to dealing with TCP/IP," Baldwin says. "When you go from a one gigabit pipe to a 10 gigabit pipe, it gets much worse. Because TCP imposes a burdensome computational load on a host, it has to be moved somewhere else."

From a user perspective, there's nothing not to like about TOE.

"Anything that optimizes the price/performance of the overall system for our clients is a good thing," says Michael Carrier, CTO and founder of infrastructure management company Totality. "This is just like miles per gallon on your car. Anything that helps us get 95 miles per gallon instead of 25, we're interested in."

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Related links:

SAN Research page

SAN Audio Primer

Storage Reviews page

Network World's Storage in the Enterprise newsletter

Other Signature Series editions

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