It is not uncommon for IT users to ask why high availability is an important quality in a web host. It is important because low redundancy or unscheduled downtime is very valuable for many businesses. Downtime represents a lost revenue generation opportunity. UK web hosting providers help clients avoid those losses. This is vital for mission-critical applications and Web-sites that must maintain always available status 24×7. The service commitments made by a provider are specified in the service level agreement (SLA) concluded with the client.
A common service offered by a UK web host is a simple fall-over server. This is essentially a reserve server that kicks into action if the main server fails. In this event, all the software applications and IP addresses that normally reside on, or are managed by, the main server are automatically transferred to the fall-over server until the main server restarts.
Redundancy and recovery time are, of course, concepts closely related to availability. This note provides a brief discussion of these concepts, beginning with redundancy. To achieve high availability, some providers adopt both passive and active redundancy strategies. Customers will benefit from a clear understanding of both these strategies.
For example, scheduled versus unscheduled downtime is a relevant distinction. It may seem somewhat counter to intuition, but scheduled downtime seems to cause more disruption than unscheduled downtime. Scheduled downtime, by definition, cannot be avoided; it must be performed at some time. The timing of the downtime is the only element that can be controlled by the management. This can be a major problem for some web hosts unless they have adequate alternative capacity that can remain in service to supply client needs during the scheduled period for the downtime capacity.
By contrast, active redundancy does not involve building-in surplus capacity but rather systems to detect failures and automatically reconfigure the network to bypass the failed items using linked computing systems. Active redundancy involves zero or no human intervention. The process is sometimes referred to as continuous system reconfiguration.
Some providers define their availability to exclude all scheduled downtime. This has the effect of raising their reported uptime performance. Providers maintain this deliberate exclusion is appropriate because scheduled repairs and maintenance downtime is non-optional and not controllable by the provider.
One point for bloggers to consider when evaluating Web hosting services is the ownership of their data or content. Many blogs are hosted on third-party managed sites like Google blogspot and WordPress. Bloggers hosted on these sites are at risk of losing their content without notice.
These blog sites have the legal right to remove all the content from a blog, without any obligation to notify the blogger, if the blog content is deemed offensive or to contravene the policy of the host.
To sum up, it is plain to understand why high availability is an important quality in a web host. High availability maximizes revenue earning opportunities. Web hosts provide service to a variety of customers including ISPs, business organizations and private individuals. They generally design the IT architecture of their hosting network to be globally distributed. Many also replicate operating zones to independent data centres around the world ensuring 100 percent availability to service client needs at all times, even during scheduled downtime.
