Cloud Computing is offered as a service model with Software,
Platform and Infrastructure as a service. It basically advocates the aspect of
Computing services as a utility. Here, all the programs and data are stored and
accessed from the internet and not from local computer.
In a traditional client-server model, basically the server is a
process which shares its resources and accepts requests from other processes
within a network to perform a service. The client is the requesting process in
that network. The clients send their requests in the form of messages to the
server to perform a particular job. The server may be a webpage or it may host
a database or it may be a series of file shares. When the client and the server
communicate, the client knows the capabilities and limitations of the server’s hardware.
These systems have to be redundant and fault tolerant in case if one server
goes down, all the clients have to be redirected to other server.
Now in the cloud model, as the server architecture i.e. hardware,
topology and the actual number of machines are abstracted from the user along
with all the uses like web server, file server, database server. The abstracted
infrastructure cannot be accessed by the user. This is not handled locally. In
the traditional model, the users access it over a private network and it is handled
The main difference between these two models is virtualization which
helps to scale out the resources based upon the needs of an organization in the
cloud model. In the traditional model, the hardware limitations limit the
number of server’s present in the system as the servers are fixed in the
hardware and it takes days to add a new server. In the cloud model, as the hardware
is offered as a service, it can be scaled out easily based on the needs of an organization.
In terms of cost, in the client server model, even if a small
resource is required from short term, all the physical equipment has to be
purchased and maintained by the user which turns out to be expensive for smaller
organizations whereas the user can just rent the resource’s that they need in
the cloud model and they only pay for what they use without any overhead of maintenance
and hardware limitations. As the services are rented rather than purchased, that
is the novelty about cloud computing as a concept.