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 A NIC in any server can become a bottleneck or single point of failure for a network. Multihoming the server with several NICs can resolve some sticky issues, but raises new questions regarding management, routing and name-binding. How does the client choose an IP host to talk to? How are clients rerouted when a NIC fails? NIC array software helps ease these concerns; it lets you bind a single network address to multiple NICs and enjoy high throughput and increased fault tolerance.

We put IP Metrics Software's NIC Express 1.0 and NSI Software's Balance Suite 2.5 to the test at our University of Wisconsin-Madison Real-World Labs®, and found they deliver substantial performance gains and fault tolerance to boot. The more CPUs and NICs, the better the performance, especially with Balance Suite.

Both Balance Suite for NT and NIC Express performed as the vendors advertised, offering load-balancing and fault-tolerance features. NIC Express delivers a bit more flexibility in configuration, but Balance Suite has better performance. We also found that Balance Suite scales a little better than NIC Express as you add NICs and processors.

NSI Software Balance Suite 2.5
Originally produced for NetWare, Balance Suite is now a great addition for Windows NT servers. It did very well in our performance tests, topping 270 Mbps of throughput. However, it isn't flexible; it supports only one NIC array per server. All NICs are added to that array automatically.

Installing Balance Suite was as simple as adding a protocol to Windows NT. We then manually configured an IP address (and other IP information). A quick look into Balance Suite's monitoring GUI showed all the NICs to be responding and handling packets. The GUI also allows you to monitor the data flow in real time, but you should reserve that application strictly for troubleshooting because it eats up valuable CPU time and slows the machine.

After getting everything up and running, we took our servers through the performance and fault-tolerance routines. Balance Suite had better performance than NIC Express at almost all data points and made better use of additional NICs and CPUs--the more the merrier. Both NIC Express and Balance Suite use a lot of CPU cycles to pump out that data.

To test fault tolerance, we simply pulled a network cable from the switch. Our Windows NT 4.0 clients noticed only a temporary glitch in the network before resuming data transfer.

IP Metrics Software NIC Express 1.0
NIC Express offers more flexibility than Balance Suite, with many more configurations, including multiple NIC arrays in the same server. Though its performance was not quite on a par with that of Balance Suite, we rate the two products' fault tolerance even. But at only $195 per server, you can't go wrong with NIC Express, unless you need a solution for NetWare servers as well.

Like Balance Suite, NIC Express is installed in NT's Network Control Panel. With it in place, we created an array and added NICs to it. If we had had more segments, we could have split the NICs among the arrays. As we added each NIC, we were asked if we wanted its configuration added to the array. The installation asked us whether to copy the NIC's information, including IP address, to the array. We only used this option for one of the NICs. From that point on, the server had one IP address but more than one NIC.

We found no glitches in client connectivity, using Windows NT 4.0, Windows95 and Macintosh clients to connect. Performance tests using Ganymede Software's Chariot showed that NIC Express doesn't scale as well as Balance Suite. NIC Express performed better in a faster machine with more CPUs, as did Balance Suite. But as the number of NICs and CPUs increased, the gap in performance between the products widened in Balance Suite's favor.

In terms of fault tolerance, NIC Express fulfilled our expectations. We ran it through some Chariot file reads and unplugged network interfaces. The file reads didn't perform very well, although the clients never lost their connections.

We suspect the performance glitch has something to do with IP Metrics Software's NDIS (Network Driver Interface Specification) implementation for the Intel Pro 100 driver. IP Metrics informs us that this driver doesn't report the card's down status very quickly.

Robert J. Kohlhepp can be reached at rkohlhepp@nwc.com.