A
web hosting service is a type of Internet hosting service that allows
individuals and organizations to make their website accessible via the
World Wide Web. Web hosts are companies that provide space on a server
owned or leased for use by clients, as well as providingInternet
connectivity, typically in a data center. Web hosts can also provide
data center space and connectivity to the Internet for other servers
located in their data center, called colocation, also known as Housing
in Latin America or France.
The
scope of web hosting services varies greatly. The most basic is web
page and small-scale file hosting, where files can be uploadedvia File
Transfer Protocol (FTP) or a Web interface. The files are usually
delivered to the Web "as is" or with minimal processing.[1] ManyInternet
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 providesdatabase
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
Multiple racks of servers
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.
A
hosting provider’s SLAs may include a certain amount of scheduled
downtime per year in order to perform maintenance on the systems. This
scheduled downtime is often excluded from the SLA timeframe, and needs
to be subtracted from the Total Time when availability is calculated.
Depending on the verbiage of an SLA, if the availability of a system
drops below that in the signed SLA, a hosting provider often will
provide a partial refund for time lost.
Types of hosting
Internet hosting services can run Web servers.
Many
large companies, which are not internet service providers, also need a
computer permanently connected to the web to send email, files, etc. to
other sites. The company may use the computer as a website host to
provide details of their goods and services and serve for online orders.
Free web hosting service: offered
by different companies with limited services, sometimes supported by
advertisements, and often limited when compared to paid hosting.
Shared web hosting service:
one's website is placed on the same server as many other sites, ranging
from a few to hundreds or thousands. Typically, all domains may share a
common pool of server resources, such as RAM and the CPU. The features
available with this type of service can be quite extensive. A shared web
may be hosted with a reseller.
Reseller web hosting: allows
clients to become web hosts themselves. Resellers could function, for
individual domains, under any combination of these listed types of
hosting, depending on who they are affiliated with as a reseller.
Resellers' accounts may vary tremendously in size: they may have their
own virtual dedicated server to a colocated server. Many resellers
provide a nearly identical service to their provider's shared hosting
plan and provide the technical support themselves.
Virtual Dedicated Server:
also known as a Virtual Private Server (VPS), divides server resources
into virtual servers, where resources can be allocated in a way that
does not directly reflect the underlying hardware. VPS will often be
allocated resources based on a one server to many VPSs relationship,
however virtualisation may be done for a number of reasons, including
the ability to move a VPS container between servers. The users may have
root access to their own virtual space. Customers are sometimes
responsible for patching and maintaining the server.
Dedicated hosting service:
the user gets his or her own Web server and gains full control over it
(user has root access for Linux/administrator access for Windows);
however, the user typically does not own the server. Another type of
Dedicated hosting is Self-Managed or Unmanaged. This is usually the
least expensive for Dedicated plans. The user has full administrative
access to the server, which means the client is responsible for the
security and maintenance of his own dedicated server.
Managed hosting service:
the user gets his or her own Web server but is not allowed full control
over it (user is denied root access for Linux/administrator access for
Windows); however, they are allowed to manage their data via FTP or
other remote management tools. The user is disallowed full control so
that the provider can guarantee quality of service by not allowing the
user to modify the server or potentially create configuration problems.
The user typically does not own the server. The server is leased to the
client.
Colocation web hosting service: similar
to the dedicated web hosting service, but the user owns the colo
server; the hosting company provides physical space that the server
takes up and takes care of the server. This is the most powerful and
expensive type of web hosting service. In most cases, the colocation
provider may provide little to no support directly for their client's
machine, providing only the electrical, Internet access, and storage
facilities for the server. In most cases for colo, the client would have
his own administrator visit the data center on site to do any hardware
upgrades or changes.
Cloud hosting:
is a new type of hosting platform that allows customers powerful,
scalable and reliable hosting based on clustered load-balanced servers
and utility billing. A cloud hosted website may be more reliable than
alternatives since other computers in the cloud can compensate when a
single piece of hardware goes down. Also, local power disruptions or
even natural disasters are less problematic for cloud hosted sites, as
cloud hosting is decentralized. Cloud hosting also allows providers to
charge users only for resources consumed by the user, rather than a flat
fee for the amount the user expects they will use, or a fixed cost
upfront hardware investment. Alternatively, the lack of centralization
may give users less control on where their data is located which could
be a problem for users with data security or privacy concerns.
Clustered hosting: having
multiple servers hosting the same content for better resource
utilization. Clustered Servers are a perfect solution for
high-availability dedicated hosting, or creating a scalable web hosting
solution. A cluster may separate web serving from database hosting
capability. (Usually Web hosts use Clustered Hosting for their Shared
hosting plans, as there are multiple benefits to the mass managing of
clients)
Grid hosting: this form of distributed hosting is when a server cluster acts like a grid and is composed of multiple nodes.
Home server: usually
a single machine placed in a private residence can be used to host one
or more web sites from a usually consumer-grade broadband connection.
These can be purpose-built machines or more commonly old PCs. Some ISPs
actively attempt to block home servers by disallowing incoming requests
to TCP port 80 of the user's connection and by refusing to provide
static IP addresses. A common way to attain a reliable DNS host name is
by creating an account with a dynamic DNS service. A dynamic DNS service
will automatically change the IP address that a URL points to when the
IP address changes.
Some specific types of hosting provided by web host service providers:
§ File hosting service: hosts files, not web pages
§ Image hosting service
§ Video hosting service
§ Blog hosting service
§ Paste bin
§ Shopping cart software
§ E-mail hosting service
Obtaining hosting
Web
hosting is often provided as part of a general Internet access plan;
there are many free and paid providers offering these types of web
hosting.
A
customer needs to evaluate the requirements of the application to
choose what kind of hosting to use. Such considerations include database
server software, scripting software, and operating system. Most hosting
providers provide Linux-based web hosting which offers a wide range of
different software. A typical configuration for a Linux server is the
LAMPplatform: Linux, Apache, MySQL, and PHP/Perl/Python. The web hosting
client may want to have other services, such as email for their
business domain, databases or multi-media services for streaming media. A
customer may also choose Windows as the hosting platform. The customer
still can choose from PHP, Perl, and Python but may also use ASP .Net or
Classic ASP. Web hosting packages often include a Web Content
Management System, so the end-user does not have to worry about the more
technical aspects.
