- By Kelly Jackson Higgins
- Jun 06, 1999
It used to be that you could bulk up on computers and power supplies to ensure that your server farm stayed up and running and was safe from outages. But old-fashioned redundancy isn't always enough these days. With the growing demands on World Wide Web and application servers, one sick server can knock all the users offline.
To solve the problem, some state and local governments are adding load-balancing technology to better distribute traffic among servers and network connections. Load balancing lets system and network administrators spread traffic among multiple Web servers so that one server isn't handling an inordinate number of requests while other servers, such as a dedicated backup or hot-standby box, sit idle. It also can stretch the existing server capacity and connection bandwidth by providing multiple connections to individual servers.
Interestingly, a popular feature of load-balancing technology among many state and local government agencies isn't the balancing part. Instead, it's pure fault tolerance. No one wants users or constituents to get an error message or to lose a connection to the server.
San Mateo County, Calif., runs load-balancing software on about 10 of its Microsoft Corp. Windows NT servers. "Load balancing wasn't our primary goal," said Chris Flatmoe, the county's advisory systems engineer. "We expected to get fault tolerance and then load balancing as a side benefit."
Most state and local government Web sites don't have the big-time traffic headaches that major corporate sites experience, so they don't need much load balancing yet. "We have a really small Web site with not much activity," said Frank Hughes, the network architect for Orange County, Fla. "We don't have the typical ISP-type problems, where you have a bunch of tiny machines you have to gang all together."
For agencies and municipalities that are adopting load balancing, it's all about reliability. That means ensuring that an agency's users will be able to access
e-mail or other applications running on servers regardless of traffic. "When you pick up the phone, you expect a dial tone. Our job is to make the Internet [and intranets] as reliable as that," said Marc Goodman, senior director of marketing for F5 Labs Inc., a Seattle-based maker of load-balancing products.
Load balancing makes it easy to add and drop servers without taking down the Web site or a key application. For instance, Arizona State University, which runs RADWare Inc.'s Web Server Director load-balancing device, can take a server out of its Web site farm and add a CPU to it without disrupting service. "It's easy for us to scale up now," said Jack Hsu, ASU's manager of systems and network management. "And it's easy to configure; all you do is add another IP address."
Another benefit: extending server bandwidth in faster 100 megabits/sec Ethernet networks. "It's a way to add bandwidth in incremental steps without jumping to Gigabit," said Scott Wieder, business manager for large enterprise marketing at 3Com Corp., which sells load-balancing products. "The only step between 100 megabits/sec Ethernet and Gigabit is load balancing."
No Deadbeat Servers
In the past year, San Mateo has been running IP Metrics Software Inc.'s NIC Express load-balancing software for its Windows NT servers. These servers host three major applications for the county: a child-support payment system that also tracks deadbeat parents, a budgeting application and a court system application.
The NIC Express software, which runs on top of the server's network interface cards (NICs), provides automatic failover if a server goes down. NIC Express basically load balances among the NICs so that if one NIC fails, another can take over without a user getting any "bump" in the application or connection. By spreading the load among NICs, the load-balancing software also increases throughput to and from the servers. Microsoft's Windows NT Server can reach about 70 megabits/sec of the 100 megabits/sec in Fast Ethernet, but with the load-balancing feature, San Mateo gets about 120 to 150 megabits/sec throughput, Flatmoe said. There are two NICs in each server. "We have two pipes bridged because of the [load-balancing] software," he said.
San Mateo has experienced a couple of failovers with its load-balancing function, including one occasion when an employee inadvertently knocked out the link to the server that runs the child-support application. The only indication of the problem was an error message on the server.
"In they eyes of the IP Metrics software, the NIC had failed," Flatmoe said. So the software automatically switched to a healthy NIC, and the child-support application kept running without the users noticing the glitch, he said.
Delaware also uses load balancing as a tool for fault tolerance and disaster recovery. But unlike San Mateo, which runs software-based load balancing on its servers, Delaware has load-balancing appliances, or dedicated devices, for three big Unix-based Sun Microsystems Inc.
Ultra e-mail and Web servers for 200 of the state's public schools.
"Originally the servers couldn't handle the load," said Glenn Wright, telecommunications technologist for the state's Office of Information Services. "We put in the load-balancing unit to handle the load, and we use it for redundancy and maintenance" as well, he said.
Before installing an F5 Labs BigIP appliance, Delaware's servers could handle a maximum of 4,700 concurrent sessions on the servers; now those servers can handle 48,000 concurrent sessions.
Quality, not Quantity
Load-balancing technology also is starting to tie in more closely with quality-of-service technologies for IP networks. QOS lets you prioritize types of traffic or applications so that an SAP America Inc. application, for instance, can take precedence over an e-mail message. Cisco Systems Inc.'s Local Director, Version 3.1, can prioritize types of traffic so that e-mail and file transfers would be considered low-priority and Web server servers would be considered high priority, for instance.
"You're going to see load balancing start to incorporate QOS so [that] you can throttle bandwidth based on applications," said Mike Long, vice president of marketing and technology at RADWare.
Load balancing definitely enhances the quality of life for network and systems managers. When a server crashes, load balancers automatically reroute traffic to a healthy connection or server. "Before, if a server went down, the network manager got paged in the middle of the night," F5's Goodman said. "That's not really a problem anymore."
Kelly Jackson Higgins is a free-lance writer and editor based in Stanardsville, Va. She can be reached at email@example.com.
Which System Is Right for You?
How do you know whether to go with a software solution, a hardware appliance or even a network switch-based load-balancing product?
Software-based load-balancing products, such as IP Metrics Software Inc.'s NIC Express, Alteon WebSystems Inc.'s ACElerate and Bright Tiger Technologies' ClusterCATS, are the most inexpensive flavor of load balancing. IP Metrics' NIC Express costs about $349 a server, compared with the price for Cisco Systems Inc.'s Local Director appliance, which costs $10,000 to $25,000.
The trade-off, however, is that many of these products are tied to the operating system. "You have to make sure the software can run on all the different operating systems, and the network manager has to configure each with that software," said Marc Goodman, senior director of marketing for F5 Labs Inc., a Seattle-based maker of load-balancing products.
David Wilbanks, co-founder, president and chief executive officer of IP Metrics, said the company's NIC Express software actually can work in conjunction with load-balancing appliances. "We load balance across multiple connections to a single machine," he said. "And we add additional layers of fault tolerance and throughput behind the device. For each server, you can now handle twice the throughput in traffic."
3Com Corp., meanwhile, packages load balancing with its Fast EtherLink Server network interface card. You can put eight of the 3Com NICs in one server. The Fast EtherLink Server NIC's price was its big selling point for Lancaster County, Pa.'s Career & Technology Center. Dean Fry, the network manager for the center, purchased his first two NIC cards for $139.
Now the center, a vocational and technical center for high school and adult education, has four of the load-balancing NIC cards for directing traffic among its file, print and Web servers. "As soon as I installed the cards, I saw drastic changes on the network," Fry said. "It almost doubled our throughput."
Load-balancing appliances, such as Cisco's Local Director, F5 Labs' BigIP, HydraWeb Technologies Inc.'s HydraWeb and RADWare Inc.'s Web Server Director, traditionally have been hot among Internet service providers, the Fortune 500 and large electronic commerce sites. But some state universities with busy Web sites, such as Arizona State University, also are plugging in the appliances.
ASU used to run a single server for its Web site, but that got risky, even with a hot standby server. "We wanted to create a single image from the user's perspective" using multiple servers, said Jack Hsu, manager of systems and network management at ASU. That way, users would see just one URL, even though there are five servers sitting behind it.
One of the more advanced features emerging in load-balancing appliances and switches is so-called global load balancing. Global load balancing is where a load balancer can send a user's server request to the nearest server. "That's not trivial; you have to measure latency, packet loss and availability," said Mike Long, vice president of marketing and technology at RADWare. The company's DS and NP options for its Web Server Director provide global load balancing, as does Cisco's Distributed Director, F5's 3DNS and Alteon's ACEdirector switches.
Then there are the switches that come packaged with load-balancing functions. Foundry Networks, 3Com and Alteon's Layer 3 Gigabit Ethernet switches come with load balancing - Foundry in its ServerIron, 3Com in its CoreBuilder 9300 and 9400s, and Alteon in its ACEdirector. The main benefit is that a switch with load-balancing functions is one less device to manage, and it's fast.
- Kelly Jackson Higgins