Become proficient in designing and building n-tier platforms and you can have high availability at low cost, says IT analysis company Meta Group.
N-tier architecture, which involves a client attaching to separate web, application and database servers, allows for “agility” and multiple points of interaction, says Meta Group Australia analyst Kevin McIsaac.
But when developing applications companies should focus on the application server rather than the web server or database server, McIsaac told a group of users at a Borland seminar in Auckland.
“Web applications are good for extending your reach to many people but a web-based application is no good for power users. And what about people coming in over the phone? If you build web-based applications you can only focus on the web. A lot of people made the mistake of focusing their development on the browser. Instead you should build one set of business logic and put it on the app server. Then the web server, telephone system, call centre, etc, can come in through it. It all comes back to the same application so you have consistency for the customer and can also build once and deploy in different ways,” he says.
McIsaac says web servers are already a commodity, and a survey by Netcraft has found that of SSL-enabled websites, Microsoft IIS has the greatest market share (50%), followed by Apache (25%), Netscape and Red Hat. This means Microsoft has won the battle of the web server, he says, but the battle for the application server continues between EJB (enterprise java beans] or COM (component object mode).
“The application server has three major parts — execution services, integrity services and gateway services. If you use the services of the application server you should be able to build a highly scalable platform. Things like load balancing, resource management, transactional integrity and security should all be in the application server,” says McIsaac.
He says development efforts today are usually based around the database but the focus is shifting to the application server. “The database is important but it’s just an SQL server dishing up data. The app server will provide the scalability and high availability.”
McIsaac says a lot of people are using n-tier architecture to build high-availability environments using low cost commodity Wintel/Lintel servers. “They are putting a load balancing router behind the firewall, which balances the load across a farm of commodity low-end web servers, and a farm of low-end application servers with application server software which is also load balancing. This is instead of using the operating system for load balancing and fail over.
“You use operating system fail over and clustering only in the data management tier. At that database tier you’re usually using something like a four-way NT box or, more likely, Unix.”
He claims by having five Intel servers, each with 95% availability, organisations can achieve a 99.999% availability — something usually only found on mainframe or high-end fault tolerant systems.