One of the most amazing things about the Web servers is that in some cases a very small machine can handle a large number of visitors. For example, imagine you have a small Web site that contains a number of static Web pages (in this case, “static” means that everyone sees the same version of any page). If you take a computer with a Celeron processor 500 MHz Windows 2008 or an Linux operating system, which loads an Apache Web server, and connect the machine to the Internet through a good connection, such as an E1 (2MB per second) or E3 (34MB per second), you could handle hundreds of thousands of daily visitors. Many ISPs can provide this type of service with a dedicated machine and for a reasonable price.
It will work beautifully unless the following occurs:
- You need to handle millions of visits daily.
- The machine in question fails. In this case your website will be down until a new machine is installed and configured.
- The Web pages are too long and complicated.
- The pages are dynamically changing on a daily basis by an interaction of users and visitors you have.
- A background process must be performed to create content on the pages or on pages processing requests.
- By meeting these conditions many most large Web sites, large and complex infrastructures are needed.
There are three main strategies to cope with a large load on web servers:
- You can invest in a single machine with a lot of processing, memory, space on hard drive and redundancy.
- The site can distribute the load through numerous machines.
- The site may use a combination of the first two options.
When you visit a site that has a different URL each time you visit, such as www1.esds.co.in, www2.esds.co.in, www3.esds.co.in, etc. then you know that the website is using alternative second access to the Web. This means that the website has a number of separate machines, where each of them is running a web publishing software for pages on them.
Requests to a Web page of domain are spread in two ways:
The DNS site can distribute the load. A DNS is an Internet service that translates domain name to IP addresses. Each time a request is made to the web server, DNS will rotate through the available IP addresses in a circular to distribute and share the load. Each of the servers has a common access to the pages of the same website.
Some switches can also distribute the load. All requests for the Web site are made to a machine and then passes the request to one of the available servers. As it has been said, and you have seen, the main advantage of this method is that there is redundancy and if some of the machines break or fall, the other will continue to work to keep the web accessible. Another advantage is that you can add capacity in an incremental way. The best way to see what suits you is to control the traffic that is coming to your website, and depending on the load you are going to need, talk to your ISP or your web hosting service provider to order a larger capacity.
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