System Area Networks to Bring More Scalability to Datacenter Server

Microsoft's forthcoming W2K Datacenter Server will enable use of the WinSock Direct Path (WSDP) API within what it calls a "system area network" to bring horizontal scalability to the operating system.

Microsoft Corp.’s forthcoming Windows 2000 Datacenter Server will enable use of the WinSock Direct Path (WSDP) API within what it calls a "system area network" to bring horizontal scalability to the operating system. The result: Companies will be able to create mainframe-class systems by stringing together Intel-based Datacenter servers.

The WinSock/SAN specification that Microsoft created with Compaq Computer Corp. last year links WinSock, the API most applications talk to when dealing with Windows NT, with interconnect technology to build system area networks.

System area networks -- not to be confused with storage area networks -- are similar to local area networks. They are, however, built for high bandwidth and low latency so groups of clustered Windows NT or Windows 2000 servers can benefit from high-speed communications.

"The whole idea is to enhance clustered communications by enabling servers to communicate directly with each other, thus improving performance," says James Gruener, managing director of Windows 2000 platforms at Aberdeen Group (, a market analyst firm.

Dan Kusnetsky, an analyst with research firm International Data Corp. (, explains that hardware has to be ready for this solution as well as the software. "Hardware is a critical piece of the system area network," he says.

To facilitate the hardware development, Microsoft is partnering with Compaq Computer Corp. and GigaNet Inc. (

"We are working to put more richness in the hardware, which eliminates layers of software," says Terry Wood, ServerNet sales manager at Compaq. "That way, we can actually bypass a good majority of the TCP/IP stack."

System area networks bypass the networking layers that are designed to ensure delivery of data over long distances via TCP/IP, most of which concentrate on preventing problems in the delivery. Since WSDP provides a direct path between servers, and because the system area network is a constrained schema where everything is local, these layers are not necessary.

"Eliminating networking layers makes the apps run faster," says Gareth Taube, vice president of worldwide marketing at GigaNet.

Michel Gambier, product manager for Windows 2000 enterprise marketing at Microsoft, says that because system area networks are built with limited cable lengths, limited topologies and a direct path between servers, the configuration is inherently secure.

Microsoft and GigaNet have a solution resulting from this initiative based on GigaNet’s cLAN (Cluster LAN) product. cLAN is a set of interconnects that can be used to hook multiple Intel servers together. The combined solution also uses the Virtual Interface (VI) architecture, a standard interface for high-speed cluster communications endorsed by Compaq, Microsoft, Intel Corp. and a host of other vendors.

The biggest drawback to VI has been that, to take full advantage of it, ISVs have to port their applications to the interface. Some vendors, such as Oracle Corp. and IBM Corp., for example, have already done so. Microsoft aims to alter this need to write to VI.

"The idea is to add the functionality of the VI standard into Datacenter," Taube says. "That enables applications written to the WinSock API to run faster without developers having to change the code."

According to Taube, test configurations show a marked improvement in performance. For example, a network call that normally requires the processing of 7,000 instructions was completed with about 50 instructions within a system area network consisting of Intel servers, Windows 2000, VI and cLAN interconnects.

Another benefit of WSDP, according to Microsoft’s Gambier, is that companies can introduce new servers to the system area network in a standard way, further improving scalability.

"Traditionally, there is a performance loss when adding processors, and the goal is to reduce and ultimately eliminate that loss," Compaq’s Wood says.

Wood pointed to a 72-node system area network that Compaq created last November with Sandia National Laboratories ( The system area network reduced the elapsed time for sorting a terabyte of data to less than 50 minutes from 150 minutes.

"Each additional server added significant compute power," Wood says. "And although 72 servers were ganged together for that project, theoretically a configuration like that could grow from just two nodes."

Gambier says the initial target markets for system area networks will be distributed applications, distributed middleware and OS services.

"Applications that require the fast moving of data between nodes are perfect environments for this system area network solution," Gambier says.

Enterprise resource planning software packages, for instance, are naturally distributed. With WSDP, the applications have a direct path to each other; they’ll be able to speak to other services -- such as a sales application on one server communicating with an inventory application on another machine -- as if the applications reside on the same machine.

Microsoft and Compaq are working toward making the WinSock/SAN initiative into an industry standard so customers will not be forced to rely on a single vendor. Ideally a customer could buy a Compaq server or a Dell server and plug it into the system area network, knowing that it will work.

Although Microsoft would not comment on exactly when the WinSock/SAN initiative will enter beta testing, the company says it will coincide with Datacenter Server entering the beta phase [estimate??].

"System area networks will have benefits down the line for all Windows 2000 products and beyond, but that is a long range process," Aberdeen’s Gruener says.