The evolution of the website structure of the common website development

I have also seen some articles about the evolution of the > website architecture, such as LiveJournal and ebay, which are very worthy of reference. But it feels like they're talking about the results of each evolution, not in detail about why they need to evolve, and how many of them feel it's hard to understand why a Web site needs so much complexity, so there's the idea of writing this article, In this article will describe a common web site to develop into a large web site in the process of a more typical architecture evolution and the knowledge system needed to master, hope to be engaged in the Internet industry students a little preliminary concept, the text of the wrong place also please give a little more advice, so that this article really played a good effect.

Architecture Evolution First Step: physical separation of webserver and databases

At first, because of some ideas, I built a website on the Internet, this time maybe even the host is leased, but because this article we only focus on the evolution of the architecture, so assume this time is already hosted a host, and has a certain bandwidth, this time because the site has a certain characteristics, Attracted some people to visit, gradually you find the system more and more pressure, response speed is more and more slow, and this time is more obvious is the database and application interaction, application problems, the database is also very easy to problem, and the database problem, the application is also easy to problem, So it goes into the first stage of evolution: separating applications and databases physically, become two machines, this time there is no new technical requirements, but you find that the effect of the system is restored to the previous response speed, and the support of higher traffic, and not because of the database and application formation of the impact of each other.
Look at the diagram of the system after this step is completed:

This step involves these knowledge systems:
The evolution of this architecture does not require basic technical knowledge systems.

Architecture Evolution Step Two: Increase page caching

Not long, with more and more people visit, you find that the response speed began to slow down, find out why, found that access to the database is too much operation, resulting in fierce competition in the data connection, so the response slowed, but the database connection can not open too much, otherwise the database machine pressure will be very high So consider adopting caching mechanism to reduce the competition of database connection resources and the pressure of database reading, this time may be the first choice to use squid and other similar mechanisms to the system of relatively static pages (such as a two-day update page) to cache (of course, you can also use the solution to the page static), This program can not be modified, it can be very good to reduce the pressure on the webserver and reduce the competition for database connection resources, OK, so began to use squid to do relatively static caching of the page.
Look at the diagram of the system after this step is completed:

This step involves these knowledge systems:
Front-End page caching technology, such as squid, if you want to use good words have to thoroughly grasp the implementation of squid and cache failure algorithm.