Overview of Cloud Computing in Distributed Systems.

Cloud computing evolves form grid computing and provides on-demand resource provisioning. Grid computing may or may not be in the cloud depending on what type of users are using it. If the users are systems administrators and integrators, they care how things are maintained in the cloud. Cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction.

What is the cloud


On-demand service — A consumer can unilaterally provide computing capabilities, such as server time and network storage, as needed automatically without requiring human interaction with each service provider.

Resource pooling — The provider’s computing resources are pooled to serve multiple consumers using a multitenant model, with different physical and virtual resources dynamically assigned and reassigned according to consumer demand

Rapid elasticity — Capabilities can be rapidly and elastically provisioned, in some cases automatically, to quickly scale out and rapidly released to quickly scale in.

Measured Service — Cloud systems automatically control and optimize resource use by leveraging a metering capability at some level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts).

Virtualization — Virtualization is a technique of resource sharing that is based on the principle of dividing physical resources(HW) or operating systems(SW)for cost control measures and more efficient utilization of resources.


Cloud Software as a Service (SaaS) — The consumer use the provider’s applications running on a cloud infrastructure. The applications are accessible from various client devices through a thin client interface such as a web browser (e.g., web-based email).

Cloud Platform as a Service (PaaS) — The consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages and tools supported by the provider.

Cloud Infrastructure as a Service (IaaS) — The consumer has the capability to provision processing, storage, networks, and other fundamental computing resources. The consumer is able to deploy and run arbitrary software, which can include operating systems and applications.

Service Models


Threshold policy: To test if the program works, develop, or improve and implement, a threshold policy in a pilot study before moving the program to the production environment. Check how the policy detects sudden increases in the demand and results in the creation of additional instances to fill in the demand. Also check to determine how unused resources are to be de-allocated and turned over to other work.

Interoperability issues: The problems of achieving interoperability of applications between two cloud computing vendors. Need to reformat data or change the logic in applications.

Hidden costs : Cloud computing does not tell what hidden costs are. In an instance of incurring network costs, companies who are far from the location of cloud providers could experience latency, particularly when there is heavy traffic.

Unexpected behavior : The tests to be made to show unexpected results of validation or releasing unused resources. Need to fix the problem before running the application in the cloud.


Though the above said challenges are existing in cloud computing, security is the major concern. Security in terms of data handling, maintaining, migrating or virtualization in clouds Security concerns in cloud are not that different from non-cloud service offerings although they are exasperated because in a single-tenant, non-cloud environment we generally know where information is and how it’s being kept.

With lots of different customers, that isolation of that data is not appropriately maintained. Providers have to manage service and isolation of potentially millions of customers and this presents a challenge as we see infrastructure and applications scale to address consumption at this level. Every cloud service provider has a different cloud model like: A Saas provider may be relying on other external providers for its backbone, infrastructure and data storage.

Cloud computing places business data into the hands of an outside provider, cloud computing makes regulatory compliance inherently riskier and more complex than it is when systems are maintained in-house. Loss of direct oversight means that client company must verify that service provider is working to ensure that the data security and integrity are ironclad.


Cloud computing though resolves many problems like mass storage area, computing, resource sharing in distributed systems, it still has many problems to solve in it. This article throws light on some of the technical security issues in cloud computing. The future work could be to find better SOA for cloud computing, complying better rules for cloud service providers, better data retrieval methods.