cloud computing module3 CLOUD COMPUTING ARCHITECTURE

CLOUD COMPUTING(21CS72)
FACULTY NAME: Prof.Chandana D C
SECTION:VII ‘A’

CLOUD COMPUTING ARCHITECTURE:
INTRODUCTION
CLOUD REFERENCE MODEL
 TYPES OF CLOUDS
 ECONOMICS OF THE CLOUD
OPEN CHALLENGES

1. INTRODUCTION
Cloud computing is a utility-oriented and Internet-centric way of delivering IT services
on demand.
These services cover the entire computing stack: from the hardware infrastructure pack-
aged as a set of virtual machines to software services such as development platforms and
distributed applications.
In most cases hardware resources are virtualized to provide isolation of workloads and
to best exploit the infrastructure.
According to the specific service delivered to the end user, different layers can be
stacked on top of the virtual infrastructure: a virtual machine manager, a development

4.2.1 Architecture
Cloud infrastructure can be heterogeneous in nature because a
variety of resources, such as clusters and even networked PCs, can
be used to build it.
Moreover, database systems and other storage services can also be
part of the infrastructure.
The physical infrastructure is managed by the core middleware, the
objectives of which are to provide an appropriate runtime
environment for applications and to best utilize resources.
At the bottom of the stack, virtualization technologies are used to
guarantee runtime environment customization, application
isolation, sandboxing, and quality of service.

Hardware virtualization is most commonly used at this level. Hypervisors manage
the pool of resources and expose the distributed infrastructure as a collection of
virtual machines.
 By using virtual machine technology it is possible to finely partition the hardware
resources such as CPU and memory and to virtualized specific devices, thus
meeting the requirements of users and applications. This solution is generally
paired
The combination of cloud hosting platforms and resources is generally classified as
a Infrastructure-as-a-Service(IaaS) solution.
IaaS solutions are suitable for designing the system infrastructure but provide
limited services to build applications
Users develop their applications specifically for the cloud by using the API exposed
at the user-levelmiddleware.
For this reason,this approach is also known as Platform-as-a-Service(PaaS)
because the service of feed to the user is a development platform rather than an
infrastructure.

4.2.2 Infrastructure- and hardware-as-a-service

Infrastructure- and Hardware-as-a-Service (IaaS/HaaS) solutions are the
most popular and developed market segment of cloud computing.
They deliver customizable infrastructure on demand.
 The available options within the IaaS offering umbrella range from single
servers to entire infrastructures, including network devices, load
balancers, and database and Web servers.
The main technology used to deliver and implement these solutions is
hardware virtualization: one or more virtual machines opportunely
configured and interconnected define the distributed system on top of
which applications are installed and deployed.
 Virtual machines also constitute the atomic components that are
deployed and priced according to the specific features of the virtual
hardware: memory, number of processors, and disk storage. IaaS/HaaS
solutions bring all the bene-fits of hardware virtualization:orkload
partitioning, application isolation, sandboxing, and hardware tuning.

Provides an overall view of the components for ming an Infrastructure-as-
a-Service solution. It is possible to distinguish three principal layers:the
physical infrastructure, the software management infrastructure, and the
user interface.
 At the to player the user inter face provides access to the services
exposed by the software management infrastructure. Such an interface is
generally based on Web 2.0 technologies: Web services, RESTful APIs, and
mash-ups.
 These technologies allow either applications or final users to access the
services exposed by the underlying infrastructure.
Web 2.0 applications allow developing full-featured management consoles
completely hosted in a browser or a Web page.

The scheduler interacts with the other
components that perform a variety of tasks:

4.2.3 Platform as a service(PAAS)

Platform-as-a-Service (PaaS) solutions provide a development and
deployment platform for running applications in the cloud.
They constitute the middleware on top of which applications are built. A
general overview of the features characterizing the PaaS approach is given in
Application management is the core functionality of the middleware.
PaaS implementations provide applications with a runtime environment
and do not expose any service for managing the underlying infrastructure.
 They automate the process of deploying applications to the infrastructure,
configuring application components, provisioning and configuring supporting
technologies such as load balancers and databases, and managing system
change based on policies set by the user.
 Developers design their systems in terms of applications and are not
concerned with hardware (physical or virtual), operating systems, and other
low-level services.

4.2.4 Software as a service (SaaS)
Software-as-a-Service (SaaS) is a software delivery model that provides access to applications
through the Internet as a Web-based service.
 It provides a means to free users from complex hardware and software management by
offloading such tasks to third parties, which build applications accessible to multiple users
through a Web browser.
 In this scenario, customers neither need install anything on their premises nor have to pay
considerable up-front costs to purchase the software and the required licenses.
 They simply access the application website, enter their credentials and billing details, and
can instantly use the application, which, in most of the cases, can be further customized for
their needs.
 On the provider side, the specific details and features of each customer’s application are
maintained in the infrastructure and made available on demand.
The SaaS model is appealing for applications serving a wide range of users and that can be
adapted to specific needs with little further customization.
This requirement characterizes SaaS as a “one-to-many” software delivery model, whereby
an application is shared across multiple users.

The analyses is carried out by SIIA was mainly oriented to cover application
service providers (ASPs) and all their variations, which capture the concept of
software applications consumed as a service in a broader sense. ASPs already
had some of the core characteristics of SaaS:
 The products old to customer is application access.
The application is centrally managed.
The service delivered is one-to-many.
The service delivered is an integrated solution delivered on the contract, which
means provided as promised.
Initially ASPs offered hosting solutions for packaged applications, which were
served to multiple customers. Successively, other options, such as Web-based
integration of third-party application services, started to gain interest and a new
range of opportunities open up to independent software vendors and service
providers

•Software cost reduction and total cost of
ownership (TCO) were paramount
• Service-level improvements
• Rapid implementation
• Standalone and configurable applications
• Rudimentary application and data integration
• Subscription and pay-as-you-go (PAYG) pricing

3. TYPES OF CLOUDS
Clouds constitute the primary outcome of cloud computing. They are a type
of parallel and distributed system harnessing physical and virtual computers
presented as a unified computing resource.
Clouds build the infrastructure on top of which services are implemented and
delivered to customers.
Such infrastructures can be of different types and provide useful information
about the nature and the services offered by the cloud.
It is then possible to differentiate four different types of cloud:
1. Public clouds
2. Private clouds.
3. Hybrid or heterogeneous clouds.
4. Community clouds.

1. Public clouds. The cloud is open to the wider public.
2. Private clouds. The cloud is implemented within the private
premises of an institution and generally made accessible to
the members of the institution or a subset of them.
3. Hybrid or heterogeneous clouds. The cloud is a combination
of the two previous solutions and most likely identifies a
private cloud that has been augmented with resources or
services hosted in a public cloud.
4. Community clouds. The cloud is characterized by a multi-
administrative domain involving different deployment
models (public, private, and hybrid), and it is specifically
designed to address the needs of a specific industry.

Public clouds
Public clouds constitute the first expression of cloud computing. They are a realization of the canonical
view of cloud computing in which the services offered are made available to anyone, from anywhere,
and at any time through the Internet.
From a structural point of view they are a distributed system, most likely composed of one or more
datacenters connected together, on top of which the specific services offered by the cloud are
implemented.
Any customer can easily sign in with the cloud provider, enter her credential and billing details, and use
the services offered.
Historically, public clouds were the first class of cloud that were implemented and offered.
They offer solutions for minimizing IT infrastructure costs and serve as a viable option for handling peak
loads on the local infrastructure.
They have become an interesting option for small enterprises, which are able to start their businesses
without large up-front investments by completely relying on public infrastructure for their IT needs.
A fundamental characteristic of public clouds is multitenancy. A public cloud is meant to serve a
multitude of users, not a single customer.
 Any customer requires a virtual computing environment that is separated, and most likely isolated, from
other users.

Private clouds
Public clouds are appealing and provide a viable option to cut IT costs and reduce
capital expenses, but they are not applicable in all scenarios.
For example, a very common critique to the use of cloud computing in its canonical
implementation is the loss of control.
In the case of public clouds, the provider is in control of the infrastructure and,
eventually, of the customers’ core logic and sensitive data.
 In particular, institutions such as government and military agencies will not
consider public clouds as an option for processing or storing their sensitive data.
The risk of a breach in the security infrastructure of the provider could expose such
information to others; this could simply be considered unacceptable.
For example, the USA PATRIOT Act5 provides its government and other agencies
with virtually limitless powers to access information, including that belonging to
any company that stores information in the U.S. territory.

Private clouds are virtual distributed systems that rely on a private
infrastructure and provide internal users with dynamic provisioning of
computing resources.
Instead of a pay-as-you-go model as in public clouds, there could be other
schemes in place, taking into account the usage of the cloud and
proportionally billing the different departments or sections of an enterprise.
Private clouds have the advantage of keeping the core business operations
in-house by relying on the existing IT infrastructure and reducing the burden
of maintaining it once the cloud has been set up.
In this scenario, security concerns are less critical, since sensitive
information does not flow out of the private infrastructure.
Moreover, existing IT resources can be better utilized because the private
cloud can provide services to a different range of users.
 Another interesting opportunity that comes with private clouds is the
possibility of testing applications and systems at a comparatively lower

Some of the key advantages of using a private
cloud computing infrastructure:
Customer information protection. Despite assurances by the public cloud leaders
about security, few provide satisfactory disclosure or have long enough histories
with their cloud offerings to provide warranties about the specific level of security
put in place on their systems. In-house security is easier to maintain and rely on.
Infrastructure ensuring SLAs. Quality of service implies specific operations such as
appropriate clustering and failover, data replication, system monitoring and
maintenance, and disaster recovery, and other uptime services can be
commensurate to the application needs. Although public cloud vendors provide
some of these features, not all of them are available as needed.
Compliance with standard procedures and operations. If organizations are subject
to third-party compliance standards, specific procedures have to be put in place
when deploying and executing applications. This could be not possible in the case
of the virtual public infrastructure.

Different options can be adopted to implement private clouds. Figure 4.4 provides
a compre hensive view of the solutions together with some reference to the most
popular software used to deploy private clouds.
At the bottom layer of the software stack, virtual machine technologies such as
Xen, KVM, and VMware serve as the foundations of the cloud.
Virtual machine management technologies such as VMware vCloud, Eucalyptus ,
and OpenNeN can be used to control the virtual infrastructure and provide an IaaS
solution. VMware vCloud is a proprietary solution, but Eucalyptus provides full
compatibility with Amazon Web Services interfaces and supports different virtual
machine technologies such as Xen, KVM, and VMware.
Like Eucalyptus, OpenNebula is an open-source solution for virtual infrastructure
man agement that supports KVM, Xen, and VMware, which has been designed to
easily integrate third-party IaaS providers.
 Its modular architecture allows extending the software with additional features
such as the capability of reserving virtual machine instances by using Haizea as
scheduler.

Hybrid clouds allow enterprises to exploit existing IT infrastructures, maintain
sensitive information within the premises, and naturally grow and shrink by
provisioning external resources and releasing them when they’re no longer needed.
Security concerns are then only limited to the public portion of the cloud that can be
used to perform operations with less stringent constraints but that are still part of the
system workload.
Figure 4.5 provides a general overview of a hybrid cloud: It is a heterogeneous
distributed system resulting from a private cloud that integrates additional services or
resources from one or more public clouds.
For this reason they are also called heterogeneous clouds. As depicted in the
diagram, dynamic provisioning is a fundamental component in this scenario. Hybrid
clouds address scalability issues by leveraging external resources for exceeding
capacity demand.
These resources or services are temporarily leased for the time required and then
released. This practice is also known as cloudbursting.

Community clouds are distributed systems created by integrating the services of different
clouds to address the specific needs of an industry, a community, or a business sector.
 The National Institute of Standards and Technologies (NIST) [43] characterizes community
clouds as follows:
The infrastructure is shared by several organizations and supports a specific community that
has shared concerns (e.g., mission, security requirements, policy, and compliance
considerations).
It may be managed by the organizations or a third party and may exist on premise or off
premise.
provides a general view of the usage scenario of community clouds, together with reference
architecture.
The users of a specific community cloud fall into a well-identified community, sharing the same
concerns or needs; they can be government bodies, industries, or even simple users, but all of
them focus on the same issues for their interaction with the cloud.
This is a different scenario than public clouds, which serve a multitude of users with different
needs.
Community clouds are also different from private clouds, where the services are generally
delivered within the institution that owns the cloud.

Candidate sectors for community clouds are as follows
1. Media industry.
In the media industry, companies are looking for low-cost, agile, and
simple solutions to improve the efficiency of content production.
Most media productions involve an extended ecosystem of partners.
In particular, the creation of digital content is the outcome of a
collaborative process that includes movement of large data, massive
compute-intensive rendering tasks, and complex workflow
executions.
Community clouds can provide a shared environment where services
can facilitate business-to-business collaboration and offer the
horsepower in term

2 Healthcare industry.
 In the healthcare industry, there are different scenarios in which community
clouds could be of use.
In particular, community clouds can provide a global platform on which to share
information and knowledge without revealing sensitive data maintained within
the private infrastructure.
 The naturally hybrid deployment model of community clouds can easily
support the storing of patient-related data in a private cloud while using the
shared infrastructure for noncritical services and automating processes within
hospitals.
3.Energy and other core industries.
In these sectors, community clouds can bundle the comprehensive set of
solutions that together vertically address management, deployment, and
orchestration of services and operations.
Since these industries involve different providers, vendors, and organizations, a
community cloud can provide the right type of infrastructure to create an open
and fair market.

The benefits of these community clouds are
the following:
Openness. By removing the dependency on cloud vendors, community clouds are open
systems in which fair competition between different solutions can happen.
Community. Being based on a collective that provides resources and services, the
infrastructure turns out to be more scalable because the system can grow simply by
expanding its user base.
Graceful failures. Since there is no single provider or vendor in control of the
infrastructure, there is no single point of failure.
Convenience and control. Within a community cloud there is no conflict between
convenience and control because the cloud is shared and owned by the community,
which makes all the decisions through a collective democratic process.
Environmental sustainability. The community cloud is supposed to have a smaller
carbon footprint because it harnesses underutilized resources. Moreover, these clouds
tend to be more organic by growing and shrinking in a symbiotic relationship to support
the demand of the community, which in turn sustains it.

3. Public sector.
Legal and political restrictions in the public sector can limit the adoption of
public cloud offerings.
Moreover, governmental processes involve several institutions and agencies
and are aimed at providing strategic solutions at local, national, and
international administrative levels.
They involve business-to-administration, citizen-to-administration, and
possibly business-to-business processes.
Some examples include invoice approval, infrastructure planning, and public
hearings. A community cloud can constitute the optimal venue to provide a
distributed environment in which to create a communication platform for
performing such operations.
4. Scientific research.
Science clouds are an interesting example of community clouds.
In this case, the common interest driving different organizations sharing a
large distributed infrastructure is scientific computing.

4 ECONOMICS OF THE CLOUD
The main drivers of cloud computing are economy of scale and
simplicity of software delivery and its operation.
In fact, the biggest benefit of this phenomenon is financial: the pay-
as-you-go model offered by cloud providers. In particular, cloud
computing allows:
Reducing the capital costs associated to the IT infrastructure
Eliminating the depreciation or lifetime costs associated with IT
capital assets
Replacing software licensing with subscriptions
Cutting the maintenance and administrative costs of IT resources

A capital cost is the cost occurred in purchasing an asset that is useful in the production
of goods or the rendering of services.
Capital costs are one-time expenses that are generally paid up front and that will
contribute over the long term to generate profit.
The IT infrastructure and the software are capital assets because enterprises require
them to conduct their business.
At present it does not matter whether the principal business of an enterprise is related
to IT, because the business will definitely have an IT department that is used to
automate many of the activities that are performed within the enterprise: payroll,
customer relationship management, enterprise resource planning, tracking and
inventory of products, and others
The amount of cost savings that cloud computing can introduce within an enterprise is
related to the specific scenario in which cloud services are used and how they contribute
to generate a profit for the enterprise. In the case of a small startup, it is possible to
completely leverage the cloud for many aspects, such as:
IT infrastructure
 Software development
CRM and ERP

5. OPEN CHALLENGES
1. Cloud definition
2. Cloud interoperability and standards
3. Scalability and fault tolerance
4. Security, trust, and privacy
5. Organizational aspects

Cloud definition
As discussed earlier, there have been several attempts made to define cloud computing and to
provide a classification of all the services and technologies identified as such.
One of the most comprehensive formalizations is noted in the NIST working definition of cloud
computing
rapid elasticity, and measured service; classifies services as SaaS, PaaS, and IaaS; and categorizes
deployment models as public, private, community, and hybrid clouds.
The view is in line with our discussion and shared by many IT practitioners and academics.
These characterizations and taxonomies reflect what is meant by cloud computing at the present
time, but being in its infancy the phenomenon is constantly ev
olving, and the same will happen to the attempts to capture the real nature of cloud computing.
It is interesting to note that the principal characterization used in this book as a reference for
introducing and explaining cloud computing is considered a working definition, which by nature
identifies something that continuously changes over time by becoming refined.

Cloud interoperability and standards

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