Availability

Often referred to as uptime, the availability of a system describes its accessibility and ability to provide a level of redundancy that works to prevent failure at any single point.  For instance, if only one server is responding to HTTP requests, the server qualifies as a single point of failure.  If there are two web servers in a load balancing scheme, then the load balancer itself is the single point of failure.  Most high availability systems are equipped with efficient fault-tolerance mechanisms to ensure the necessary redundancies.  Because 100% availability is costly and rather difficult to achieve, the industry standard in the web hosting business is at around 99.9%.

Load Balancing

Load balancing is a method web hosting providers employ to more evenly distribute the system load over a group of available servers.  This technology is used to ensure that all servers process their fair share of requests without being overworked and more susceptible to failing.  There are many types of load balancers and these mechanisms come in both software and hardware varieties.

Response time and Transaction Load

The performance of a server is associated with the response time of a given transaction load.  In regard to a website, it is measured by the time it takes to load web pages and process requests to the web server.  The performance of large, high traffic websites can be greatly enhanced by upgrading hardware, residing on a dedicated server or utilizing load balancing technology.  In many cases, fine tuning software packages such as MySQL and PHP can also increase response times.

Scalability

The scalability of a system generally refers to the property that enables it to service any given load by upgrading hardware or incorporating additional services in a predetermined manner.  It essentially describes an instance in which performance and throughput can still be maintained once the load increases.  Scalability is a great quality to have in a web hosting solution as it can support the growth and increasing needs of your website.

Session State

Session state is often needed to maintain the connection of a client program and a given server.  This typically needs to be done to accommodate a user who is logged into the system.  If the topology consists of multiple servers, maintaining session state is crucial and something that must be taken care.  Most load balancing software applications on the market provide facilities that enable this to done.  The most common methods are implementing cookies and rewriting URLs with the server details included.  load_balance.htm

Throughput

Though closely tied to performance, throughput is best described as the number of concurrent transactions the server is able to process.  The higher the throughput, the more processing power to the system.

Related posts:

• October 2, 2011 – How Much RAM / Bandwidth / Disk Space Do I Really Need?
• September 29, 2011 – Guarantees – Separating Fact from Fiction
• June 6, 2011 – Surviving Website Downtime
• May 9, 2011 – Knowing When to Choose a Cloud Hosting Plan
• April 14, 2011 – The Transition from Shared Hosting to the Cloud
• February 17, 2011 – When to Cancel a Web Hosting Plan
• January 16, 2011 – What Makes a Top Web Hosting Site?
• January 16, 2011 – Web Server Uptime – a Key to the Selection of the Best Web Hosting Company
• January 13, 2011 – Learn about Web Hosting with its Offers
• January 13, 2011 – How to Select the Best Web Hosting Company?