The scope of web hosting services varies greatly. The most basic is web page and small-scale file hosting, where files can be uploaded via File Transfer Protocol (FTP) or a Web interface. The files are usually delivered to the Web "as is" or with minimal processing.[1] Many Internet service providers (ISPs) offer this service free to subscribers. Individuals and organizations may also obtain Web page hosting from alternative service providers. Personal web site hosting is typically free, advertisement-sponsored, or inexpensive. Business web site hosting often has a higher expense.
Single page hosting is generally sufficient for personal web pages. A complex site calls for a more comprehensive package that provides database support and application development platforms (e.g. PHP, Java, Ruby on Rails, ColdFusion, or ASP.NET). These facilities allow customers to write or install scripts for applications like forums and content management. Also, Secure Sockets Layer (SSL) is typically used for e-commerce.
The host may also provide an interface or control panel for managing the Web server and installing scripts, as well as other modules and service applications like e-mail. Some hosts specialize in certain software or services (e.g. e-commerce), which are commonly used by larger companies that outsource network infrastructure.
Reliability and uptime
The availability of a website is measured by the percentage of a year in which the website is publicly accessible and reachable via the internet. This is different than measuring the uptime of a system. Uptime refers to the system itself being online, however it does not take into account being able to reach it as in the event of a network outage.
The formula to determine a system’s availability is relatively easy: Total time = 365 days per year * 24 hours per day * 60 minutes per hour = 525,600 minutes per year. To calculate how many minutes of downtime a system may experience per year, take the uptime guarantee and multiply it by total time in a year.
In the example of 99.99%: (1 - .9999) * 525,600 = allowable minutes down per year.
The following table shows the translation from a given availability percentage to the corresponding amount of time a system would be unavailable per year, month, or week.
Availability % | Downtime per year | Downtime per month* | Downtime per week |
---|---|---|---|
90% ("one nine") | 36.5 days | 72 hours | 16.8 hours |
95% | 18.25 days | 36 hours | 8.4 hours |
97% | 10.96 days | 21.6 hours | 5.04 hours |
98% | 7.30 days | 14.4 hours | 3.36 hours |
99% ("two nines") | 3.65 days | 7.20 hours | 1.68 hours |
99.5% | 1.83 days | 3.60 hours | 50.4 minutes |
99.8% | 17.52 hours | 86.23 minutes | 20.16 minutes |
99.9% ("three nines") | 8.76 hours | 43.2 minutes | 10.1 minutes |
99.95% | 4.38 hours | 21.56 minutes | 5.04 minutes |
99.99% ("four nines") | 52.56 minutes | 4.32 minutes | 1.01 minutes |
99.999% ("five nines") | 5.26 minutes | 25.9 seconds | 6.05 seconds |
99.9999% ("six nines") | 31.5 seconds | 2.59 seconds | 0.605 seconds |
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