osting reliability and uptime.

Hosting uptime refers to the percentage of time the host is accessible via the internet. Many providers state that they aim for a 99.9% uptime, but there may be server restarts and planned (or unplanned) maintenance in any hosting environment. A common claim from the popular hosting providers is ’99% or 99.9% server uptime’ but this often refers only to a server being powered on and doesn’t account for network downtime. Real downtime can potentially be larger than the percentage guaranteed by the provider. Many providers tie uptime and accessibility into their own service level agreement (SLA). SLAs sometimes include refunds or reduced costs if performance goals are not met.

Types of hosting

• A typical server “rack,” commonly seen in colocation centres. Internet hosting services can run Web servers; see Internet hosting services. Hosting services limited to the Web:
• Free web hosting service:
  It is free, (sometimes) advertisement-supported web hosting, and is often limited when compared to paid hosting.
• Shared web hosting service:
  one’s Web site 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 website 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 provider. 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:
  dividing a server into virtual servers, where each user feels like they’re on their own dedicated server, but they’re actually sharing a server with many other users. The users may have root access to their own virtual space. This is also known as a virtual private server or VPS. 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 (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 box, which means the client is responsible for the security and maintenance of his own dedicated box.
• Managed hosting service:
  the user gets his or her own Web server but is not allowed full control over it (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 the 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.
• 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. * 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 hostname 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.