Cloud computing is a general term for anything that involves
delivering hosted services over the Internet. These services are broadly
divided into three categories: Infrastructure-as-a-Service (IaaS),
Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS). The name
cloud computing was inspired by the cloud symbol that's often used to
represent the Internet in flowcharts and diagrams.
Cloud computing
comes into focus only when you think about what IT always needs: a way
to increase capacity or add capabilities on the fly without investing in
new infrastructure, training new personnel, or licensing new software.
Cloud computing encompasses any subscription-based or pay-per-use
service that, in real time over the Internet, extends IT's existing
capabilities.
There's a good chance you've already used some form
of cloud computing. If you have an e-mail account with a Web-based
e-mail service like Hotmail, Yahoo! Mail or Gmail, then you've had some
experience with cloud computing. Instead of running an e-mail program on
your computer, you log in to a Web e-mail account remotely. The
software and storage for your account doesn't exist on your computer --
it's on the service's computer cloud.
Cloud Computing Architecture
What makes up a cloud computing system?
When
talking about a cloud computing system, it's helpful to divide it into
two sections: the front end and the back end. They connect to each other
through a network, usually the Internet. The front end is the side the
computer user, or client, sees. The back end is the "cloud" section of
the system.
The front end includes the client's computer (or
computer network) and the application required to access the cloud
computing system. Not all cloud computing systems have the same user
interface. Services like Web-based e-mail programs leverage existing Web
browsers like Internet Explorer or Firefox. Other systems have unique
applications that provide network access to clients.
On the back
end of the system are the various computers, servers and data storage
systems that create the "cloud" of computing services. In theory, a
cloud computing system could include practically any computer program
you can imagine, from data processing to video games. Usually, each
application will have its own dedicated server. A central server
administers the system, monitoring traffic and client demands to ensure
everything runs smoothly. It follows a set of rules called protocols and
uses a special kind of software called middleware. Middleware allows
networked computers to communicate with each other. Most of the time,
servers don't run at full capacity.
If a cloud computing company
has a lot of clients, there's likely to be a high demand for a lot of
storage space. Some companies require hundreds of digital storage
devices. Cloud computing systems need at least twice the number of
storage devices it requires to keep all its clients' information stored.
That's because these devices, like all computers, occasionally break
down. A cloud computing system must make a copy of all its clients'
information and store it on other devices. The copies enable the central
server to access backup machines to retrieve data that otherwise would
be unreachable. Making copies of data as a backup is called redundancy.
Service Models
Cloud
computing providers offer their services according to three fundamental
models: Infrastructure as a service (IaaS), platform as a service
(PaaS), and software as a service (SaaS) where IaaS is the most basic
and each higher model abstracts from the details of the lower models.
Infrastructure as a Service (IaaS)
In this most basic cloud service model, cloud providers offer computers – as physical or more often as virtual machines –, raw (block) storage, firewalls, load balancers, and networks. IaaS providers supply these resources on demand from their large pools installed in data centers. Local area networks including IP addresses are part of the offer. For the wide area connectivity, the Internet can be used or - in carrier clouds - dedicated virtual private networks can be configured.
To
deploy their applications, cloud users then install operating system
images on the machines as well as their application software. In this
model, it is the cloud user who is responsible for patching and
maintaining the operating systems and application software. Cloud
providers typically bill IaaS services on a utility computing basis,
that is, cost will reflect the amount of resources allocated and
consumed.
Platform as a Service (PaaS)
In the PaaS model, cloud providers deliver a computing platform and/or solution stack typically including operating system, programming language execution environment, database, and web server. Application developers can develop and run their software solutions on a cloud platform without the cost and complexity of buying and managing the underlying hardware and software layers. With some PaaS offers, the underlying compute and storage resources scale automatically to match application demand such that the cloud user does not have to allocate resources manually.
Software as a Service (SaaS)
In this model, cloud providers install and operate application software in the cloud and cloud users access the software from cloud clients. The cloud users do not manage the cloud infrastructure and platform on which the application is running. This eliminates the need to install and run the application on the cloud user's own computers simplifying maintenance and support. What makes a cloud application different from other applications is its elasticity. This can be achieved by cloning tasks onto multiple virtual machines at run-time to meet the changing work demand. Load balancers distribute the work over the set of virtual machines. This process is transparent to the cloud user who sees only a single access point. To accomodate a large number of cloud users, cloud applications can be multitenant, that is, any machine serves more than one cloud user organization. It is common to refer to special types of cloud based application software with a similar naming convention: desktop as a service, business process as a service, Test Environment as a Service, communication as a service.
Cloud storage advantages
- Companies need only pay for the storage they actually use as it is also possible for companies by utilizing actual virtual storage features like thin provisioning.
- Companies do not need to install physical storage devices in their own datacenter or offices, but the fact that storage has to be placed anywhere stays the same (maybe localization costs are lower in offshore locations).
- Storage maintenance tasks, such as backup, data replication, and purchasing additional storage devices are offloaded to the responsibility of a service provider, allowing organizations to focus on their core business, but the fact stays the same that someone has to pay for the administrative effort for these tasks
- Cloud storage provides users with immediate access to a broad range of resources and applications hosted in the infrastructure of another organization via a web service interface.
Six Benefits of Cloud Computing :
- Reduced Cost
Cloud technology is paid incrementally, saving organizations money.
- Increased Storage
Organizations can store more data than on private computer systems.
- Highly Automated
No longer do IT personnel need to worry about keeping software up to date.
- Flexibility
Cloud computing offers much more flexibility than past computing methods.
- More Mobility
Employees can access information wherever they are, rather than having to remain at their desks.
- Allows IT to Shift Focus
No
longer having to worry about constant server updates and other
computing issues, government organizations will be free to concentrate
on innovation.
source: wikipedia
No comments:
Post a Comment