Microsoft Accelerates iSCSI Support

Microsoft today finally delivered its TCP Chimney Technology designed to alleviate a performance bottleneck on processors -- a move that IP SAN system and chipmakers hope will make 10-Gbit/s iSCSI a legitimate rival to Fibre Channel. (See Microsoft Dusts Off Chimney.)

Chimney support comes as part of the Microsoft Windows Server 2003 Scalable Networking Pack (SNP) Microsoft said today at its Windows Hardware Engineering Conference (WinHEC). SNP is a service pack that lets Windows Server 2003 users take advantage of hardware-enabled TCP/IP offload. SNP also includes Receive Side Scaling (RSS), another feature that should give 10-Gbit iSCSI a boost.

TCP Chimney will offload CPU-intensive packet processing to TCP/IP offload engines (TOEs), providing a large performance boost over the Microsoft software initiator that handles offload on most current iSCSI SANs. Receive Side Scaling (RSS) lets the TCP stack run on multiple processors, which Linux and Unix allow but hasn't been possible on Windows till now.

While early IP SAN adopters find the Windows software initiator adequate for Gigabit Ethernet, it is not expected to be able to handle the full load of 10-GigE. (See 10G Supply Exceeds Demand.)

"This is critical to widespread adoption of 10GigE and iSCSI," analyst Bob Wheeler of the Linley Group says of SNP. "There's a huge performance benefit in being able to do TCP in hardware, especially with storage applications that deal with huge large blocks of data.Microsoft originally expected to have TCP Chimney ready to go last year, but its release was delayed when Alacritech filed for patent infringement. The sides settled last July with Microsoft agreeing to license the technology. (See Alacritech, MSFT, B'com Cross-License .)

Alacritech, Broadcom, Chelsio Communications, and NetXen today said they are supporting SNP, with all but Chelsio specifically mentioning the Chimney protocol. (See Alacritech Accelerates Microsoft, Broadcom, Microsoft Connect, and Chelsio Supports Microsoft.)

According to Chelsio CEO Kianoosh Naghshineh, it's only a matter of adding a driver to its existing TCP/IP offload (TOE) cards for Chimney. He plans to support Chimney, but won't say when.

"We're being vague on this, but we definitely plan to support Chimney," Chelsio CEO Kianoosh Naghshineh says. "We'll announce it when it's ready to ship. Today's the first day there is a market."

Wheeler expects other TOE vendors such as Neterion and Silverback Systems as well as Myricom to fully support SNP. (See Silverback Hoists $16M.) Neterion is demonstrating its RSS support at WinHec, but its cards do not do full TCP/IP offload and will require additional hardware to make it work."I expect all offload card vendors with the exception of Intel to support Chimney," Wheeler reports.

Intel is using I/O Acceleration Technology (I/OAT), which does TCP offloading right in the processor. Microsoft SNP also supports I/OAT and other direct memory access technologies.

Dave Raffo, News Editor, Byte and Switch

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