Unit 9 Section A

Mobile and Cloud Computing

I. Introduction

Cloud computing has been defined differently by many users and designers. IBM, a major player in cloud computing, has defined it as follows: “A cloud is a pool of virtualized computer resources. A cloud can host a variety of different workloads, including batch-style backend jobs and interactive and user-facing applications.”

The concept of cloud computing has evolved from cluster, grid, and utility computing. Cluster and grid computing leverage the use of many computers in parallel to solve problems of any size. Utility and Software as a Service (SaaS) provide computing resources as a service with the notion of pay per use. Cloud computing leverages dynamic resources to deliver large numbers of services to end users. Cloud computing is a high-throughput computing (HTC) paradigm whereby the infrastructure provides the services through a large data center or server farms. The cloud computing model enables users to share access to resources from anywhere at any time through their connected devices.

The cloud will free users to focus on user application development and create business value by outsourcing job execution to cloud providers. In this scenario, the computations (programs) are sent to where the data is located, rather than copying the data millions of desktops as in the traditional approach. Cloud computing avoids large data movement, resulting in much better network bandwidth utilization. Furthermore, machine virtualization has enhanced resource utilization, increased application flexibility, and reduced the total cost of using virtualized data-center resources.

The cloud offers significant benefit to IT companies by freeing them from the low-level task of setting up the hardware (servers) and managing the system software. Cloud computing applies a virtual platform with elastic resources put together by on-demand provisioning of hardware, software, and data sets, dynamically. The main idea is to move desktop computing to a service-oriented platform using server clusters and huge databases at data centers. Cloud computing leverages its low cost and simplicity to benefit both providers and users. Cloud computing intends to leverage multitasking to archive higher throughput by serving many heterogeneous applications, large or small, simultaneously.

II. Public, Private, and Hybrid Clouds

A public cloud is built over the Internet and can be accessed by any user who paid for the service. Public clouds are owned by service providers and are accessible through a subscription. The callout box in top of Figure 1 shows the architecture of a typical public cloud. Many public clouds are available, including Google App Engine (GAE), Amazon Web Services (AWS), Microsoft Azure, IBM Blue Cloud, and Salesforce.com’s Force.com. The providers of the aforementioned clouds are commercial providers that offer a publicly accessible remote interface for creating and managing VM instances within their proprietary infrastructure. A public cloud delivers a selected set of business processes. The application and infrastructure services are offered on a flexible price-per-use basis.

A private cloud is built within the domain of an intranet owned by a single organization. Therefore, it is client owned and managed, and its access is limited to the owning clients and their partners. Its deployment was not meant to sell capacity over the Internet through publicly accessible interfaces. Private clouds give local users a flexible and agile private infrastructure to run service workloads within their administrative domains. A private cloud is supposed to deliver more efficient and convenient cloud services. It may impact the cloud standardization, while retaining greater customization and organizational control. Intranet-based private clouds are linked to public clouds to get additional resources.

A hybrid cloud is built with both public and private clouds, as shown at the lower-left corner of Figure 1. Private clouds can also support a hybrid cloud model by supplementing local infrastructure with computing capacity from an external public cloud. For example, the Research Compute Cloud (RC2) is a private cloud, build by IBM, that interconnects the computing and IT resources at eight IBM Research Centers scattered throughout the United States, Europe, and Asia. A hybrid cloud provides access to clients, the partner network, and third parties.

In summary, public clouds promote standardization, preserve capital investment, and offer application flexibility. Private clouds attempt to archive customization and offer higher efficiency, resiliency, security, and privacy. Hybrid clouds operate in the middle, with many compromises in terms of resource sharing.

III. Cloud Design Objectives

Despite the controversy surrounding the replacement of desktop or deskside computing by centralized computing and storage services at data centers or big IT companies, the cloud computing community has reached some consensus on what has to be done to make cloud computing universally acceptable. The following list highlights six design objectives for cloud computing:

• Shifting computing from desktops to data centers: Computer processing, storage, and software delivery is shifted away from desktops and local servers and toward data centers over the Internet.
• Service provisioning and cloud economics: Providers supply cloud services by signing service-level agreements (SLAs) with consumers and end users. The services must be efficient in terms of computing, storage, and power consumption. Pricing is based on a pay-as-you-go policy.
• Scalability in performance: The cloud platforms and software and infrastructure services must be able to scale in performance as the number of users increases.

… to be continued …