Server Load Balancing

Many of today's most challenging server load balancing issues involve recognizing and understanding the nature of individual application requests and responses. Zeus Extensible Traffic Manager can read and understand requests, and then load-balance them across a pool of servers using one of a variety of intelligent load-balancing algoritms.

Resilient Load Balancing

A typical fault-tolerant cluster
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ZXTM allows you to create a fully fault-tolerant cluster of server machines by protecting against failures of back-end server nodes and front-end traffic manager units. Providing that sufficient balancer and server machines are functioning, the cluster will continue to operate without failure.

If a server goes down, you need to know that your web sites will keep running. ZXTM can seamlessly handle server failure, redirecting traffic to a different, healthy machine without your customer ever knowing. What's more, because ZXTM can be deployed in a horizontally-scalable TrafficCluster™, if a traffic manager unit is unavailable, another unit will automatically handle the traffic until the problem is fixed.

Quick Links

How can ZXTM ease the administration of my cluster? 

ZXTM has a comprehensive and intuitive graphical user interface, allowing the management of multiple traffic managers and clusters of servers. It is very easy to add or remove machines from the load-balanced cluster, balance new services, or to modify the content inspection rules.

The user interface provides comprehensive monitoring and diagnostics tools, allowing you to detect and diagnose a wide range of problems with any component of your load-balanced cluster. You can even configure an external alerting service so that details of problems can be reported immediately by email to a nominated system administrator.

How does ZXTM compare with a hardware load balancing solution? 

ZXTM is a pure software application. It is built on top of the same high-performance core architecture as the award-winning Zeus Web Server and Zeus Extensible Traffic Manager.

As a result of its application awareness, ZXTM is best deployed close to the servers it is managing. If you need to make sophisticated traffic management decisions, and need to closely monitor the health of the services you are hosting, ZXTM is optimally suited for this environment.

ZXTM offers far more than a traditional load balancing solution. Its traffic management capabilities bring much more flexibility and fine-grained application layer control than is possible with most pure- hardware load balancing solutions. Because ZXTM supports a range of platforms and operating systems and runs on commodity hardware, its performance can easily and cost-effectively be grown as required.

Does ZXTM introduce a single point of failure? 

A single front-end ZXTM can introduce a single point of failure to a load-balanced cluster. The ZXTM software is designed to operate in a robust manner, but should the hardware or operating system fail for whatever reason, your load-balanced cluster would be unavailable. However, this risk is not acceptable.

Fault-tolerant clusters ensure service continuity

The solution is to run a fault-tolerant cluster of front-end machines. The machines monitor each other, and can take over from each other if the other should fail.

This is achieved by floating Traffic IP addresses. The load balancers receive traffic on these IP addresses, and each load balancer in a fault-tolerant pair monitors its partner. If one machine were to fail, the other balancer machine takes over its Traffic IP address.

This fail-over behavior is completely transparent; any clients that subsequently use the cluster get no indication that a machine has failed and fail-over has occurred. When the first balancer recovers, it regains its Traffic IP address and the second balancer relinquishes it.

What are the benefits of a high-availability cluster? 

Donna Scott, a Gartner analyst remarks:

"Despite the Internet driving a significantly increased desire for continuous availability, through 2005, fewer than 20% of mission-critical Web-based applications will achieve it."

Studies have shown that service downtime, even for relatively brief periods, cause major losses of revenue, staff hours, and customer confidence. It is therefore no longer acceptable to be running mission-critical or revenue-generating services without some kind of redundancy built-in.

By deploying a fault-tolerant pair of ZXTMs, and ensuring that there is sufficient redundancy in your server farm, you can protect yourself against hardware or software failures in your load balanced cluster.

How does ZXTM protect back-end services? 

ZXTM provides fail-over management of back-end services. If you had four back-end servers and one was to fail, ZXTM will automatically direct all network traffic to the remaining three servers.

© Zeus Technology Ltd