Those of you with Fast Ethernet networks who've just blown your budgets on brand-new, fully loaded quad-processor servers packing terabytes of RAM know where we're coming from. Slow networks can really jam up robust servers, but many companies can't afford or don't want to upgrade. Switched Ethernet can increase your network performance, but can carry you only so far. You need something better than 100 Mbps. Fortunately, there is a very low-cost solution: By installing multiple network cards and load-balancing among them, you can achieve greater throughput. As an added bonus, you'll have fault tolerance in case one of your network connections goes down.
Nothin' but (Ether)Net
Servers are constantly getting faster, but networks don't get upgraded as quickly. Nowadays, even low-end machines easily output data at 100 Mbps, and a top-flight server can churn out a gigabit of data per second. But Gigabit Ethernet is used chiefly on the backbone, and extending even a single gigabit link to your server may be prohibitively expensive. Moreover, with only one connection, you get no fault tolerance.
So most department-level file or application servers probably run on 100-Mbps links. This means that 10 simultaneous users each get data-transfer speeds of less than 10 Mbps. That's a waste of server resources. But what if your server has four network ports, with each port able to run at 100 Mbps, thus giving each user data transfers of approximately 40 Mbps? (That's assuming, of course, that your backbone or switches can handle 400 Mbps.) Now each user could download data four times faster than before. Your people would be happy, but you'd be stuck with four different IP addresses per server. How do you know which port is the least busy? And you'll have the hassle of administering four IP addresses instead of just one.
A better solution is to have all the network cards in a single server operate as a team -- thus the term teaming NICs. TNICs share the load under one common identity, with four adapters load-balancing under a single IP address. This is also known as link aggregation or, sometimes, trunking. Of course, you need a switch (or multiple hubs) for load-balancing; otherwise, you'd get virtually no speed increase. Fortunately, switches are cheap. And TNICs are available for more than just Fast Ethernet: You can team a wide variety of flavors, including token ring.
A side benefit of load-balancing is automatic fault tolerance. If one link goes down, the load is redistributed among the remaining cards until the link comes back up. In a four-adapter situation, you can have as many as three links go down and still maintain connectivity. High-reliability systems will use links to different switches in case an entire switch goes down. All the products we tested may be configured to do only fault tolerance, and you can use fault tolerance on a hub if you so desire. We focused chiefly on load-balancing in our performance tests, which were conducted at our Syracuse University Real-World Labs® in Syracuse, N.Y.
Go Team
Four vendors participated in this review: Adaptec, with the DuraLAN Quartet64 with Duralink64; Intel Corp., with the Intel Pro/100 S Server Adapter with Advanced Network Services; IP Metrics Software, with the NIC Express for NT 2.02 and NIC Express for Windows 2000 2.12; and 3Com Corp., with the 3Com EtherLink Server Dual Port 10/100 PCI (3C982-TXM) with DynamicAccess card. While three of the vendors make network cards, drivers and accompanying load-balancing software, IP Metrics offers only load-balancing software, which runs on top of any network card. We consulted IP Metrics and, for our benchmarks, tested NIC Express using the Intel cards.
Our plan was to team up four ports and see how fast the systems could go. The hardware vendors did something interesting: They each sent cards with different numbers of ports. Intel sent four single-port cards, 3Com sent two dual-port cards and Adaptec sent a quad-port card. Thus, we needed four, two or one free PCI slot, respectively. The load-balancing software the hardware vendors supplied works on multiple versions of their products. For example, the software used to test the 3Com dual-port card will work on its single-port server adapters as well. Not all cards are supported, however, so check with the vendor to see if the card you want to buy supports the load-balancing drivers you're running.
All the products tested support multiple groups. A group is a set of cards that work together. For example, a server may contain two fault-tolerant groups with two cards per group, four cards total. Group 1 may be used for the finance department, Group 2 for the engineers. This provides the flexibility of setting up a server across multiple network segments.
Cost is also a key consideration. Even the least expensive servers can pump out more than 100 Mbps. Instead of plunging into Gigabit Ethernet, fiber or ATM, you can team standard Fast Ethernet cards on switched networks to increase bandwidth and reliability on the cheap. Indeed, prices on these products are very low: Fault tolerance alone is definitely a bargain for as little as $350. And who among us has never had a server go down because someone disconnected its Ethernet connection?
All Aboard the NIC Express
After testing these products on a dual-processor server under a variety of operating systems, we found their performance and download rates to be about on a par with one another. Therefore, it was the cards' extra features that tipped the scales. 3Com and IP Metrics provided the only solutions that support switch-independent incoming load-balancing. All the TNICs support Cisco Systems FEC (Fast EtherChannel), a protocol for teaming network cards. If your users will mostly be uploading data to the server and you don't have an FEC-compatible switch, you'll want to use 3Com's or IP Metrics' products. But if you're slot-constrained, Adaptec's card offers the best solution -- unless the card dies, in which case you're dead in the water. Intel's product has the best user interface, making it very easy not only to see which cards are in which group but also to rearrange groups. Plus, Intel is the only vendor in this roundup to offer load-balancing software for Linux. Considering Linux's growing popularity as a file and Web server, this gives Intel an added advantage.
Picking a winner was difficult because all the products did quite well, but after extensive testing, we gave our Editor's Choice award to IP Metrics. The NIC Express solution leads the pack with advanced fault-tolerance capabilities, including the ability to sense logical breaks, such as routing issues, and it can keep a flaky connection in a down state until the problem is fixed. This could be useful if a wire becomes loose and connectivity drops in and out, theoretically causing massive retransmits. On the downside, as the NIC Express is software, you will need to buy Ethernet cards separately, and most hardware vendors give away load-balancing software. Nevertheless, for only a bit of extra money, NIC Express provides a lavish collection of features. IP Metrics also provides load-balancing and fault tolerance for token-ring networks, just in case you have any of those hanging around.
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