Clustered hosting is the newest way of hosting your website. A cluster is a group of computers or servers, whose combined computational power provides a service.
Clustered hosting is a type of web hosting that spreads the
load of hosting across multiple physical machines, or node, increasing
availability and decreasing the chances of one service (e.g., FTP or email)
affecting another (e.g., MySQL). Many large websites run on clustered hosting
solutions, for example, large discussion forums will tend to run using multiple
front-end webservers with multiple back-end database servers.
most hosting infrastructures are based on the paradigm of using a single
physical machine to host multiple hosted services, including web, database,
email, FTP and others. A single physical machine is not only a single point of
failure, but also has finite capacity for traffic, that in practice can be
troublesome for a busy website or for a website that is experiencing transient
bursts in traffic.
By clustering services across multiple hardware
machines and using load balancing, single points of failure can be eliminated,
increasing availability of a website and other web services beyond that of
ordinary single server hosting. A single server can require periodic reboots for
software upgrades and the like, whereas in a clustered platform you can stagger
the restarts such that the service is still available whilst still upgrading all
necessary machines in the cluster.
Clustered hosting involves spreading
the website across multiple servers, like layers. In the CatN stack each layer
does its own individual task, so one for web, one for databases, one for logging
etc. This has one considerable advantage, if one server goes down the others
On a traditional hosting server, all of the data is stored and run
on a single layer, the main server. If this server goes down, breaks, or just
stops working then all of your website goes down with it. Nothing works, runs or
displays. How can this be prevented? By separating hosting services across a
An obvious advantage to clustering is the even distribution of
traffic across several servers, making it is less likely that a single server
will go down due to overload, and improving performance as traffic is managed.
Database activity is isolated from the web traffic, and so an increase in
database computation has minimal effect on static content form a web server, and
equally web traffic for dynamic content will have little effect on database
This separation prevents errors on one section of the
cluster from preventing other services. If an entire database service fails
(unlikely with multiple nodes), visitors to your website will still see the
static and dynamic content, but just be unable to access the database. You can
use this to your advantage by displaying a notice letting them know that the
database server is not functioning and to be patient while its being fixed. As
you can imagine, this is a lot more informative than them seeing a 404 because
the whole site has gone down from one error.
However, this separation is
not infallible. If the front-end layer goes down (static and dynamic content
servers), then no user info can be displayed. Its no good to the end user just
having the database and back-end working when there is nothing to interact with
it. Fortunately the clustered platform lends itself to stability with multiple
nodes (servers) in each layer picking up the strain if single nodes fail. New
nodes can replace failed units with no interruption to the service of your
In the CatN stack traffic is directed to the correct server
using load balancing pairs and the .craccess and .htaccess files. The load
balance pairs between service layers ensures even distribution of traffic, and
the .craccess and .htaccess files enable requests to be passed between the
static and dynamic layers in the stack.
So the low down on clustered
hosting. A cluster is the group of servers that make up the website. Each of
these servers has a dedicated job – database/web/email etc. If one server goes
down, the others don’t go down with it.