Web Hosting - Advanced Terminology
Published: Friday, February 13, 2004
Performance of a system is related to the response time for a given transaction load. For a website, performance is measured in terms of the time it takes to load pages and process requests by the server. For high traffic websites, performance can be improved by upgrading server hardware, or using a group of load balanced server. Often performance tuning of the website code (such as database SQL, efficient coding and garbage collection etc.) can enhance the response rates.
Throughput, although related to performance, more precisely is defined by the number of concurrent transactions that can be processed by the system. A higher throughput would mean more processing power of the system.
Scalability of a system is the property which allows the system to service any given load by adding additional servers or upgrading hardware to the system in a predeterminated fashion. Scalability determines whether the performance and throughput can be maintained when the load increases.
Load balancing is a technique used to distribute the load of a system among the available servers or machines, so that all the servers get their fair share of incoming requests. Read more ....
Availability (Uptime Guarantee)
Availability of a system allows it to provide redundancy in order to eliminate any single points of failure of the system. For example, if only one web server responds to the HTTP requests, the web server is a single point of failure. If two web servers are load balanced by a load balancer, the load balancer is a single point of failure. High availability systems have good fault-tolerance mechanisms in place by employing hardware and software based redundancies. However, achieving 100% availability is often very costly as compared to 99.5%. In the hosting industry this is also known as uptime guarantee.
Often it is required to maintaining the connection of a client to a particular server, as in the case of a logged in user. If there are multiple web servers in the topology, maintaining session state is a crucial consideration to be taken care of. Usually most load balancing software solutions provides a way to do this, either by implementing cookies or re-writing URLs with the server information included.