UNIT - I.docx

191AIE503T CLOUD COMPUTING UNIT - I
Department of AI&DS V-Sem Mrs.K.P.Revathi/AP,AI&DS
UNIT –I
INTRODUCTION
Introduction to Cloud Computing – Roots of Cloud Computing – Desired Features of Cloud
Computing – Challenges and Risks – Benefits and Disadvantages of Cloud Computing. –
Public, Private and Hybrid Clouds – IaaS – PaaS – SaaS – Architectural Design Challenges –
Cloud Storage- benefits and considerations of using cloud services
Introduction to Cloud Computing
The term cloud refers to a network or the internet. It is a technology that uses remote servers on the
internet to store, manage, and access data online rather than local drives. The data can be anything
such as files, images, documents, audio, video, and more.
There are the following operations that we can do using cloud computing:
 Developing new applications and services
 Storage, back up, and recovery of data
 Hosting blogs and websites
 Delivery of software on demand
 Analysis of data
 Streaming videos and audios
Cloud computing offers platform independency, as the software is not required to be installed
locally on the PC. Hence, the Cloud Computing is making our business applications mobile and
collaborative.
Why Cloud Computing?
 Small as well as large IT companies, follow the traditional methods to provide the IT
infrastructure. That means for any IT company, we need a Server Room that is the basic
need of IT companies.
 In that server room, there should be a database server, mail server, networking, firewalls,
routers, modem, switches, QPS (Query Per Second means how much queries or load will

be handled by the server), configurable system, high net speed, and the maintenance
engineers.
 To establish such IT infrastructure, we need to spend lots of money. To overcome all these
problems and to reduce the IT infrastructure cost, Cloud Computing comes into existence.
Basic Concepts
There are certain services and models working behind the scene making the cloud computing
feasible and accessible to end users. Following are the working models for cloud computing:
 Deployment Models
 Service Models
Deployment Models
Deployment models define the type of access to the cloud, i.e., how the cloud is located? Cloud
can have any of the four types of access: Public, Private, Hybrid, and Community.
Cloud Computing Deployment Models
Public Cloud
The public cloud allows systems and services to be easily accessible to the general public. Public
cloud may be less secure because of its openness.
Private Cloud
The private cloud allows systems and services to be accessible within an organization. It is more
secured because of its private nature.
Community Cloud
The community cloud allows systems and services to be accessible by a group of organizations.
Hybrid Cloud
The hybrid cloud is a mixture of public and private cloud, in which the critical activities are
performed using private cloud while the non-critical activities are performed using public cloud.
Service Models
Cloud computing is based on service models. These are categorized into three basic service
models which are -
 Infrastructure-as–a-Service (IaaS)
 Platform-as-a-Service (PaaS)
 Software-as-a-Service (SaaS)

Anything-as-a-Service (XaaS) is yet another service model, which includes Network-as-a-
Service, Business-as-a-Service, Identity-as-a-Service, Database-as-a-Service or Strategy-as-a-
Service.
The Infrastructure-as-a-Service (IaaS) is the most basic level of service. Each of the service
models inherit the security and management mechanism from the underlying model, as shown in
the following diagram:
Infrastructure-as-a-Service (IaaS)
IaaS provides access to fundamental resources such as physical machines, virtual machines,
virtual storage, etc.
Platform-as-a-Service (PaaS)
PaaS provides the runtime environment for applications, development and deployment tools, etc.
Software-as-a-Service (SaaS)
SaaS model allows to use software applications as a service to end-users.
Characteristics of Cloud Computing
There are four key characteristics of cloud computing. They are shown in the following diagram:

Cloud Computing characteristics
On Demand Self Service
Cloud Computing allows the users to use web services and resources on demand. One can logon to
a website at any time and use them.
Broad Network Access
Since cloud computing is completely web based, it can be accessed from anywhere and at any time.
Resource Pooling
Cloud computing allows multiple tenants to share a pool of resources. One can share single physical
instance of hardware, database and basic infrastructure.
Rapid Elasticity
It is very easy to scale the resources vertically or horizontally at any time. Scaling of resources
means the ability of resources to deal with increasing or decreasing demand.
The resources being used by customers at any given point of time are automatically monitored.
Measured Service
In this service cloud provider controls and monitors all the aspects of cloud service. Resource
optimization, billing, and capacity planning etc. depend on it.

Roots of Cloud Computing
The roots of cloud computing are sub-divided into four types. They are,
 Internet Technologies
 Hardware
 System Management
 Distributed Computing
Internet Technologies in Cloud Computing
Virtualization and Service-Oriented Architecture
Virtualization is the process of deploying virtual resources in cloud infrastructures such as
servers, storage management, and desktop. To reduce the cost and time effort of cloud
providers this virtualization concept is introduced. Virtualization is subdivided into various
types. The below-mentioned picture describes the various types of virtualization used in cloud
computing
Desktop Virtualization
Desktop Virtualization is the concept of users accessing their desktops virtually from any
location. For the end-user environment, this desktop virtualization is created. The types of
desktop virtualization are as follows,
Virtual desktop Infrastructure-The actions are done in the central server which provides the
virtual desktop service to the end-user.
Remote desktop Services-Users are allowed to work based on windows applications remotely
Desktop as a Service-In Desktop as a Service, a third party hosts the virtual application

Application Virtualization
In application virtualization, the users are all allowed to use the application in the system rather
than one which is installed. The OS and system software are installed on many computers.
Network Virtualization
The combination of both hardware and software operations is called Network Virtualization. It
establishes a connection between the application and the software system.
Storage Virtualization
The storage virtualization array consists of multiple arrays which are appeared to be single
virtualization. It can be either called a disk array or a storage array.
Server Virtualization
Partitioning the single server into multiple servers which can run on their independent operating
system.
Service-Oriented Architecture (SOA)
As the business grows, there is a large number of implementation of software and hardware
requirements, which is difficult to manage. Hence SOA helps to maintain and implement the
architecture.
Grid Computing
To manage and handle a large set of data, the networked computers are connected to perform
the operations. The group of computers joins as a cluster to simplify the task.
Utility Computing
As the name itself denotes, the providers provide the computing service based on the user’s
demand. It is based on the process of pay peruse.
Platform As A Service (PAAS)
As the name itself indicates “platform” means it gives a complete technical platform to the
customer such as hardware, software, and infrastructure for developing and deploying the
application. The advantage of PAAS is, that it supplies networking, storage, server, operating
system (OS), etc.., a complete cloud platform to the user for developing and running their
application without worrying about building and maintaining the cloud infrastructure required
to develop and launch the app.
Infrastructure as a service (IAAS)
It is purely an infrastructure-based cloud computing service that provides complete
infrastructure like supporting web applications, and services based on user facility. As it is
based o storage and infrastructure the customer has to use this on by pay-as-you-go basis based

on their demand. It reduces the cost of buying and managing physical servers and data
infrastructures. It increases the scale and performance of IT workloads and reduces the
expenditure on buying external hardware tools. Examples of IAAS are Amazon Web Services,
Google compute engine (GCE), Green Cloud Technologies, and Microsoft Azure.
Software as a Service (SAAS)
SAAS enables the end-user to use cloud-based applications utilizing the web. It is defined as
“On-Demand Software “hosted by the cloud service provider. The users are allowed to
subscribe to those cloud-based applications than purchasing. The users were given login
credentials to use those applications which are running on cloud servers. One of the simple and
easiest examples is Gmail.
Hardware
The hardware components of cloud computing include,
 Storage array
o Switches
 Router
 Firewall
 Backup devices
 Servers
 Load balancers
System Management
Cloud management consists of public, private, and hybrid clouds. Cloud computing performs
the overall control and work of the system.
Public cloud: The public cloud is common to everyone and is easily accessible by anyone. It
is provided over the internet to general people or major industry groups. Simple examples are
Gmail and Google drive.
Private cloud: The difference between public and private is, that the latter ensures the privacy
and security of the data through firewalls and internet hosting. If large IT organizations and
business groups are looking for secure cloud options, the best option is the Private cloud.
Examples of private clouds are Amazon Web Services, IBM, VMware, and Microsoft azure.
Multi-cloud: The name itself indicates partial meaning that the organization uses one or more
cloud services such as public and private cloud or both public and private cloud. Examples of
multi-cloud are Amazon Web Services (AWS), Google Cloud Platform (GCP), and IBM.
Hybrid cloud: The difference between multi and hybrid cloud is that the latter combines two
or more different types of the cloud while multi-clouds combines different clouds of the same
type. Examples include Azure Stack, Azure arc, and Google antos.
Distributed Computing

Distributed Computing is the connection of one or more several computers which are connected
to form a network to share information. A wide number of computers are connected to a single
network. Examples include the Internet and Gmail.
Desired Features of Cloud Computing
Features of Cloud Computing
Following are the characteristics of Cloud Computing:
1. Resources Pooling
It means that the Cloud provider pulled the computing resources to provide services to
multiple customers with the help of a multi-tenant model. There are different physical and
virtual resources assigned and reassigned which depends on the demand of the customer.
The customer generally has no control or information over the location of the provided
resources but is able to specify location at a higher level of abstraction
2. On-Demand Self-Service

It is one of the important and valuable features of Cloud Computing as the user can
continuously monitor the server uptime, capabilities, and allotted network storage. With this
feature, the user can also monitor the computing capabilities.
3. Easy Maintenance
The servers are easily maintained and the downtime is very low and even in some cases, there
is no downtime. Cloud Computing comes up with an update every time by gradually making it
better.
The updates are more compatible with the devices and perform faster than older ones along
with the bugs which are fixed.
4. Large Network Access
The user can access the data of the cloud or upload the data to the cloud from anywhere just
with the help of a device and an internet connection. These capabilities are available all over
the network and accessed with the help of internet.
5. Availability
The capabilities of the Cloud can be modified as per the use and can be extended a lot. It
analyzes the storage usage and allows the user to buy extra Cloud storage if needed for a very
small amount.
6. Automatic System
Cloud computing automatically analyzes the data needed and supports a metering capability at
some level of services. We can monitor, control, and report the usage. It will provide
transparency for the host as well as the customer.
7. Economical
It is the one-time investment as the company (host) has to buy the storage and a small part of
it can be provided to the many companies which save the host from monthly or yearly costs.
Only the amount which is spent is on the basic maintenance and a few more expenses which
are very less.
8. Security
Cloud Security, is one of the best features of cloud computing. It creates a snapshot of the data
stored so that the data may not get lost even if one of the servers gets damaged.
The data is stored within the storage devices, which cannot be hacked and utilized by any other
person. The storage service is quick and reliable.
9. Pay as you go
In cloud computing, the user has to pay only for the service or the space they have utilized.
There is no hidden or extra charge which is to be paid. The service is economical and most of
the time some space is allotted for free.
10. Measured Service

Cloud Computing resources used to monitor and the company uses it for recording. This
resource utilization is analyzed by supporting charge-per-use capabilities.
This means that the resource usages which can be either virtual server instances that are running
in the cloud are getting monitored measured and reported by the service provider. The model
pay as you go is variable based on actual consumption of the manufacturing organization.
Challenges and Risks
Cloud computing, an emergent technology, has placed many challenges in different aspects of
data and information handling. Some of these are shown in the following diagram:
Security and Privacy
Security and Privacy of information is the biggest challenge to cloud computing. Security and
privacy issues can be overcome by employing encryption, security hardware and security
applications.
Portability
This is another challenge to cloud computing that applications should easily be migrated from
one cloud provider to another. There must not be vendor lock-in. However, it is not yet made
possible because each of the cloud provider uses different standard languages for their
platforms.

Interoperability
It means the application on one platform should be able to incorporate services from the other
platforms. It is made possible via web services, but developing such web services is very
complex.
Computing Performance
Data intensive applications on cloud requires high network bandwidth, which results in high
cost. Low bandwidth does not meet the desired computing performance of cloud application.
Reliability and Availability
It is necessary for cloud systems to be reliable and robust because most of the businesses are
now becoming dependent on services provided by third-party.
The Security Risks of Cloud Computing
Cloud computing provides various advantages, such as improved collaboration, excellent
accessibility, Mobility, Storage capacity, etc. But there are also security risks in cloud
computing.
Some most common Security Risks of Cloud Computing are given below-
Data Loss
Data loss is the most common cloud security risks of cloud computing. It is also known as data
leakage. Data loss is the process in which data is being deleted, corrupted, and unreadable by
a user, software, or application. In a cloud computing environment, data loss occurs when our
sensitive data is somebody else's hands, one or more data elements can not be utilized by the
data owner, hard disk is not working properly, and software is not updated.
Hacked Interfaces and Insecure APIs
As we all know, cloud computing is completely depends on Internet, so it is compulsory to
protect interfaces and APIs that are used by external users. APIs are the easiest way to
communicate with most of the cloud services. In cloud computing, few services are available
in the public domain. These services can be accessed by third parties, so there may be a chance
that these services easily harmed and hacked by hackers.
Data Breach
Data Breach is the process in which the confidential data is viewed, accessed, or stolen by the
third party without any authorization, so organization's data is hacked by the hackers.
Vendor lock-in
Vendor lock-in is the of the biggest security risks in cloud computing. Organizations may face
problems when transferring their services from one vendor to another. As different vendors
provide different platforms, that can cause difficulty moving one cloud to another.
Increased complexity strains IT staff

Migrating, integrating, and operating the cloud services is complex for the IT staff. IT staff
must require the extra capability and skills to manage, integrate, and maintain the data to the
cloud.
Spectre & Meltdown
Spectre & Meltdown allows programs to view and steal data which is currently processed on
computer. It can run on personal computers, mobile devices, and in the cloud. It can store the
password, your personal information such as images, emails, and business documents in the
memory of other running programs.
Denial of Service (DoS) attacks
Denial of service (DoS) attacks occur when the system receives too much traffic to buffer the
server. Mostly, DoS attackers target web servers of large organizations such as banking sectors,
media companies, and government organizations. To recover the lost data, DoS attackers
charge a great deal of time and money to handle the data.
Account hijacking
Account hijacking is a serious security risk in cloud computing. It is the process in which
individual user's or organization's cloud account (bank account, e-mail account, and social
media account) is stolen by hackers. The hackers use the stolen account to perform
unauthorized activities.
Benefits and Disadvantages of Cloud Computing
Advantages of Cloud Computing
As we all know that Cloud computing is trending technology. Almost every company switched
their services on the cloud to rise the company growth.
Here, we are going to discuss some important advantages of Cloud Computing-

1) Back-up and restore data
Once the data is stored in the cloud, it is easier to get back-up and restore that data using the
cloud.
2) Improved collaboration
Cloud applications improve collaboration by allowing groups of people to quickly and easily
share information in the cloud via shared storage.
3) Excellent accessibility
Cloud allows us to quickly and easily access store information anywhere, anytime in the whole
world, using an internet connection. An internet cloud infrastructure increases organization
productivity and efficiency by ensuring that our data is always accessible.
4) Low maintenance cost
Cloud computing reduces both hardware and software maintenance costs for organizations.
5) Mobility
Cloud computing allows us to easily access all cloud data via mobile.
6) IServices in the pay-per-use model
Cloud computing offers Application Programming Interfaces (APIs) to the users for access
services on the cloud and pays the charges as per the usage of service.
7) Unlimited storage capacity

Cloud offers us a huge amount of storing capacity for storing our important data such as
documents, images, audio, video, etc. in one place.
8) Data security
Data security is one of the biggest advantages of cloud computing. Cloud offers many advanced
features related to security and ensures that data is securely stored and handled.
Disadvantages of Cloud Computing
A list of the disadvantage of cloud computing is given below -
1) Internet Connectivity
As you know, in cloud computing, every data (image, audio, video, etc.) is stored on the cloud,
and we access these data through the cloud by using the internet connection. If you do not have
good internet connectivity, you cannot access these data. However, we have no any other way
to access data from the cloud.
2) Vendor lock-in
Vendor lock-in is the biggest disadvantage of cloud computing. Organizations may face
problems when transferring their services from one vendor to another. As different vendors
provide different platforms, that can cause difficulty moving from one cloud to another.
3) Limited Control
As we know, cloud infrastructure is completely owned, managed, and monitored by the service
provider, so the cloud users have less control over the function and execution of services within
a cloud infrastructure.
4) Security
Although cloud service providers implement the best security standards to store important
information. But, before adopting cloud technology, you should be aware that you will be
sending all your organization's sensitive information to a third party, i.e., a cloud computing
service provider. While sending the data on the cloud, there may be a chance that your
organization's information is hacked by Hackers.
Types of Cloud
There are the following 4 types of cloud that you can deploy according to the organization's
needs-

Public Cloud
Public cloud is open to all to store and access information via the Internet using the pay-per-
usage method.
In public cloud, computing resources are managed and operated by the Cloud Service Provider
(CSP).
o Public Cloud provides a shared platform that is accessible to the general
public through an Internet connection.
o Public cloud operated on the pay-as-per-use model and administrated by the third
party, i.e., Cloud service provider.
o In the Public cloud, the same storage is being used by multiple users at the same time.
o Public cloud is owned, managed, and operated by businesses, universities,
government organizations, or a combination of them.
o Amazon Elastic Compute Cloud (EC2), Microsoft Azure, IBM's Blue Cloud, Sun
Cloud, and Google Cloud are examples of the public cloud.

Example: Amazon elastic compute cloud (EC2), IBM SmartCloud Enterprise, Microsoft,
Google App Engine, Windows Azure Services Platform.
Advantages of Public Cloud
There are the following advantages of Public Cloud -
o Public cloud is owned at a lower cost than the private and hybrid cloud.
o Public cloud is maintained by the cloud service provider, so do not need to worry about
the maintenance.
o Public cloud is easier to integrate. Hence it offers a better flexibility approach to
consumers.
o Public cloud is location independent because its services are delivered through the
internet.
o Public cloud is highly scalable as per the requirement of computing resources.

o It is accessible by the general public, so there is no limit to the number of users.
Disadvantages of Public Cloud
o Public Cloud is less secure because resources are shared publicly.
o Performance depends upon the high-speed internet network link to the cloud provider.
o The Client has no control of data.
Private Cloud
Private cloud is also known as an internal cloud or corporate cloud. It is used by
organizations to build and manage their own data centers internally or by the third party. It can
be deployed using Opensource tools such as Openstack and Eucalyptus.
o Private cloud is also known as an internal cloud or corporate cloud.
o Private cloud provides computing services to a private internal network (within the
organization) and selected users instead of the general public.
o Private cloud provides a high level of security and privacy to data through firewalls
and internal hosting. It also ensures that operational and sensitive data are not accessible
to third-party providers.
o HP Data Centers, Microsoft, Elastra-private cloud, and Ubuntu are the example of a
private cloud.

Based on the location and management, National Institute of Standards and Technology (NIST)
divide private cloud into the following two parts-
o On-premise private cloud
o Outsourced private cloud
Advantages of Private Cloud
There are the following advantages of the Private Cloud -
o Private cloud provides a high level of security and privacy to the users.
o Private cloud offers better performance with improved speed and space capacity.
o It allows the IT team to quickly allocate and deliver on-demand IT resources.
o The organization has full control over the cloud because it is managed by the
organization itself. So, there is no need for the organization to depends on anybody.
o It is suitable for organizations that require a separate cloud for their personal use and
data security is the first priority.
Disadvantages of Private Cloud
o Skilled people are required to manage and operate cloud services.
o Private cloud is accessible within the organization, so the area of operations is limited.
o Private cloud is not suitable for organizations that have a high user base, and
organizations that do not have the prebuilt infrastructure, sufficient manpower to
maintain and manage the cloud.

Hybrid Cloud
Hybrid Cloud is a combination of the public cloud and the private cloud. we can say:
Hybrid Cloud = Public Cloud + Private Cloud
Hybrid cloud is partially secure because the services which are running on the public cloud can
be accessed by anyone, while the services which are running on a private cloud can be accessed
only by the organization's users.
o The main aim to combine these cloud (Public and Private) is to create a unified,
automated, and well-managed computing environment.
o In the Hybrid cloud, non-critical activities are performed by the public
cloud and critical activities are performed by the private cloud.
o Mainly, a hybrid cloud is used in finance, healthcare, and Universities.
o The best hybrid cloud provider companies are Amazon, Microsoft, Google,
Cisco, and NetApp.
Example: Google Application Suite (Gmail, Google Apps, and Google Drive), Office 365
(MS Office on the Web and One Drive), Amazon Web Services.

Advantages of Hybrid Cloud
There are the following advantages of Hybrid Cloud -
o Hybrid cloud is suitable for organizations that require more security than the public
cloud.
o Hybrid cloud helps you to deliver new products and services more quickly.
o Hybrid cloud provides an excellent way to reduce the risk.
o Hybrid cloud offers flexible resources because of the public cloud and secure resources
because of the private cloud.
Disadvantages of Hybrid Cloud
o In Hybrid Cloud, security feature is not as good as the private cloud.
o Managing a hybrid cloud is complex because it is difficult to manage more than one
type of deployment model.
o In the hybrid cloud, the reliability of the services depends on cloud service providers.
Community Cloud
Community cloud allows systems and services to be accessible by a group of several
organizations to share the information between the organization and a specific community. It
is owned, managed, and operated by one or more organizations in the community, a third party,
or a combination of them.
Example: Health Care community cloud
Advantages of Community Cloud
There are the following advantages of Community Cloud -

o Community cloud is cost-effective because the whole cloud is being shared by several
organizations or communities.
o Community cloud is suitable for organizations that want to have a collaborative cloud
with more security features than the public cloud.
o It provides better security than the public cloud.
o It provdes collaborative and distributive environment.
o Community cloud allows us to share cloud resources, infrastructure, and other
capabilities among various organizations.
Disadvantages of Community Cloud
o Community cloud is not a good choice for every organization.
o Security features are not as good as the private cloud.
o It is not suitable if there is no collaboration.
o The fixed amount of data storage and bandwidth is shared among all community
members.
Difference between public cloud, private cloud, hybrid cloud, and community cloud -
The below table shows the difference between public cloud, private cloud, hybrid cloud, and
community cloud.
Parameter Public Cloud Private Cloud Hybrid Cloud Community Cloud
Host Service provider Enterprise (Third
party)
Enterprise (Third party) Community (Third party)
Users General public Selected users Selected users Community members
Access Internet Internet, VPN Internet, VPN Internet, VPN
Owner Service provider Enterprise Enterprise Community

Cloud Service Models
There are the following three types of cloud service models -
1. Infrastructure as a Service (IaaS)
2. Platform as a Service (PaaS)
3. Software as a Service (SaaS)
Infrastructure as a Service | IaaS
Iaas is also known as Hardware as a Service (HaaS). It is one of the layers of the cloud computing
platform. It allows customers to outsource their IT infrastructures such as servers, networking,
processing, storage, virtual machines, and other resources. Customers access these resources on the
Internet using a pay-as-per use model.
In traditional hosting services, IT infrastructure was rented out for a specific period of time, with pre-
determined hardware configuration. The client paid for the configuration and time, regardless of the
actual use. With the help of the IaaS cloud computing platform layer, clients can dynamically scale
the configuration to meet changing requirements and are billed only for the services actually used.
IaaS cloud computing platform layer eliminates the need for every organization to maintain the IT
infrastructure.
IaaS is offered in three models: public, private, and hybrid cloud. The private cloud implies that the
infrastructure resides at the customer-premise. In the case of public cloud, it is located at the cloud
computing platform vendor's data centre, and the hybrid cloud is a combination of the two in which
the customer selects the best of both public cloud or private cloud.

IaaS provider provides the following services -
1. Compute: Computing as a Service includes virtual central processing units and virtual
main memory for the Vms that is provisioned to the end- users.
2. Storage: IaaS provider provides back-end storage for storing files.
3. Network: Network as a Service (NaaS) provides networking components such as
routers, switches, and bridges for the Vms.
4. Load balancers: It provides load balancing capability at the infrastructure layer.
Advantages of IaaS cloud computing layer
There are the following advantages of IaaS computing layer -
1. Shared infrastructure
IaaS allows multiple users to share the same physical infrastructure.
2. Web access to the resources
Iaas allows IT users to access resources over the internet.
3. Pay-as-per-use model
IaaS providers provide services based on the pay-as-per-use basis. The users are required to
pay for what they have used.
4. Focus on the core business
IaaS providers focus on the organization's core business rather than on IT infrastructure.
5. On-demand scalability
On-demand scalability is one of the biggest advantages of IaaS. Using IaaS, users do not worry
about to upgrade software and troubleshoot the issues related to hardware components.

Disadvantages of IaaS cloud computing layer
1. Security
Security is one of the biggest issues in IaaS. Most of the IaaS providers are not able to provide
100% security.
2. Maintenance & Upgrade
Although IaaS service providers maintain the software, but they do not upgrade the software
for some organizations.
3. Interoperability issues
It is difficult to migrate VM from one IaaS provider to the other, so the customers might face
problem related to vendor lock-in.
Platform as a Service | PaaS
Platform as a Service (PaaS) provides a runtime environment. It allows programmers to easily
create, test, run, and deploy web applications. You can purchase these applications from a cloud
service provider on a pay-as-per use basis and access them using the Internet connection. In PaaS,
back end scalability is managed by the cloud service provider, so end- users do not need to worry
about managing the infrastructure.
PaaS includes infrastructure (servers, storage, and networking) and platform (middleware,
development tools, database management systems, business intelligence, and more) to support the
web application life cycle.

Example: Google App Engine, Force.com, Joyent, Azure.
PaaS providers provide the Programming languages, Application frameworks, Databases, and
Other tools:
1. Programming languages
PaaS providers provide various programming languages for the developers to develop the
applications. Some popular programming languages provided by PaaS providers are Java, PHP,
Ruby, Perl, and Go.
2. Application frameworks
PaaS providers provide application frameworks to easily understand the application
development. Some popular application frameworks provided by PaaS providers are Node.js,
Drupal, Joomla, WordPress, Spring, Play, Rack, and Zend.
3. Databases
PaaS providers provide various databases such as ClearDB, PostgreSQL, MongoDB, and Redis
to communicate with the applications.
4. Other tools
PaaS providers provide various other tools that are required to develop, test, and deploy the
applications.
Advantages of PaaS
There are the following advantages of PaaS -
1) Simplified Development

PaaS allows developers to focus on development and innovation without worrying about
infrastructure management.
2) Lower risk
No need for up-front investment in hardware and software. Developers only need a PC and an
internet connection to start building applications.
3) Prebuilt business functionality
Some PaaS vendors also provide already defined business functionality so that users can avoid
building everything from very scratch and hence can directly start the projects only.
4) Instant community
PaaS vendors frequently provide online communities where the developer can get the ideas to
share experiences and seek advice from others.
5) Scalability
Applications deployed can scale from one to thousands of users without any changes to the
applications.
Disadvantages of PaaS cloud computing layer
1) Vendor lock-in
One has to write the applications according to the platform provided by the PaaS vendor, so
the migration of an application to another PaaS vendor would be a problem.
2) Data Privacy
Corporate data, whether it can be critical or not, will be private, so if it is not located within the
walls of the company, there can be a risk in terms of privacy of data.
3) Integration with the rest of the systems applications
It may happen that some applications are local, and some are in the cloud. So there will be
chances of increased complexity when we want to use data which in the cloud with the local
data.
PaaS Types
Based on the functions, PaaS can be classified into four types as shown in the following
diagram:

Stand-alone development environments
The stand-alone PaaS works as an independent entity for a specific function. It does not
include licensing or technical dependencies on specific SaaS applications.
Application delivery-only environments
The application delivery PaaS includes on-demand scaling and application security.
Open platform as a service
Open PaaS offers an open source software that helps a PaaS provider to run applications.
Add-on development facilities
The add-on PaaS allows to customize the existing SaaS platform.
Software as a Service | SaaS
SaaS is also known as "On-Demand Software". It is a software distribution model in which services
are hosted by a cloud service provider. These services are available to end-users over the internet so,
the end-users do not need to install any software on their devices to access these services.
There are the following services provided by SaaS providers -
Business Services - SaaS Provider provides various business services to start-up the business. The
SaaS business services include ERP (Enterprise Resource Planning), CRM (Customer Relationship
Management), billing, and sales.
Document Management - SaaS document management is a software application offered by a third
party (SaaS providers) to create, manage, and track electronic documents.
Example: Slack, Samepage, Box, and Zoho Forms.
Social Networks - As we all know, social networking sites are used by the general public, so social
networking service providers use SaaS for their convenience and handle the general public's
information.
Mail Services - To handle the unpredictable number of users and load on e-mail services, many e-
mail providers offering their services using SaaS.

Advantages of SaaS cloud computing layer
1) SaaS is easy to buy
SaaS pricing is based on a monthly fee or annual fee subscription, so it allows organizations to access
business functionality at a low cost, which is less than licensed applications.
Unlike traditional software, which is sold as a licensed based with an up-front cost (and often an
optional ongoing support fee), SaaS providers are generally pricing the applications using a
subscription fee, most commonly a monthly or annually fee.
2. One to Many
SaaS services are offered as a one-to-many model means a single instance of the application is shared
by multiple users.
3. Less hardware required for SaaS
The software is hosted remotely, so organizations do not need to invest in additional hardware.
4. Low maintenance required for SaaS
Software as a service removes the need for installation, set-up, and daily maintenance for the
organizations. The initial set-up cost for SaaS is typically less than the enterprise software. SaaS
vendors are pricing their applications based on some usage parameters, such as a number of users
using the application. So SaaS does easy to monitor and automatic updates.
5. No special software or hardware versions required
All users will have the same version of the software and typically access it through the web browser.
SaaS reduces IT support costs by outsourcing hardware and software maintenance and support to the
IaaS provider.
6. Multidevice support

SaaS services can be accessed from any device such as desktops, laptops, tablets, phones, and thin
clients.
7. API Integration
SaaS services easily integrate with other software or services through standard APIs.
8. No client-side installation
SaaS services are accessed directly from the service provider using the internet connection, so do not
need to require any software installation.
Disadvantages of SaaS cloud computing layer
1) Security
Actually, data is stored in the cloud, so security may be an issue for some users. However, cloud
computing is not more secure than in-house deployment.
2) Latency issue
Since data and applications are stored in the cloud at a variable distance from the end-user, there is a
possibility that there may be greater latency when interacting with the application compared to local
deployment. Therefore, the SaaS model is not suitable for applications whose demand response time
is in milliseconds.
3) Total Dependency on Internet
Without an internet connection, most SaaS applications are not usable.
4) Switching between SaaS vendors is difficult
Switching SaaS vendors involves the difficult and slow task of transferring the very large data files
over the internet and then converting and importing them into another SaaS also.
Open SaaS and SOA
Open SaaS uses those SaaS applications, which are developed using open source programming
language. These SaaS applications can run on any open source operating system and database. Open
SaaS has several benefits listed below:
 No License Required
 Low Deployment Cost
 Less Vendor Lock-in
 More portable applications
 More Robust Solution
The following diagram shows the SaaS implementation based on SOA:

Architectural Design Challenges
Cloud computing architecture is a combination of service-oriented architecture and event-
driven architecture.
Cloud computing architecture is divided into the following two parts -
o Front End
o Back End
The below diagram shows the architecture of cloud computing -

Front End
The front end is used by the client. It contains client-side interfaces and applications that are
required to access the cloud computing platforms. The front end includes web servers (including
Chrome, Firefox, internet explorer, etc.), thin & fat clients, tablets, and mobile devices.
Back End
The back end is used by the service provider. It manages all the resources that are required to
provide cloud computing services. It includes a huge amount of data storage, security mechanism,
virtual machines, deploying models, servers, traffic control mechanisms, etc.
Components of Cloud Computing Architecture
There are the following components of cloud computing architecture -
1. Client Infrastructure
Client Infrastructure is a Front end component. It provides GUI (Graphical User Interface) to
interact with the cloud.
2. Application
The application may be any software or platform that a client wants to access.
3. Service

A Cloud Services manages that which type of service you access according to the client’s
requirement.
Cloud computing offers the following three type of services:
i. Software as a Service (SaaS) – It is also known as cloud application services. Mostly, SaaS
applications run directly through the web browser means we do not require to download and install
these applications. Some important example of SaaS is given below –
Example: Google Apps, Salesforce Dropbox, Slack, Hubspot, Cisco WebEx.
ii. Platform as a Service (PaaS) – It is also known as cloud platform services. It is quite similar
to SaaS, but the difference is that PaaS provides a platform for software creation, but using SaaS,
we can access software over the internet without the need of any platform.
Example: Windows Azure, Force.com, Magento Commerce Cloud, OpenShift.
iii. Infrastructure as a Service (IaaS) – It is also known as cloud infrastructure services. It is
responsible for managing applications data, middleware, and runtime environments.
Example: Amazon Web Services (AWS) EC2, Google Compute Engine (GCE), Cisco Metapod.
4. Runtime Cloud
Runtime Cloud provides the execution and runtime environment to the virtual machines.
5. Storage
Storage is one of the most important components of cloud computing. It provides a huge amount
of storage capacity in the cloud to store and manage data.
6. Infrastructure
It provides services on the host level, application level, and network level. Cloud infrastructure
includes hardware and software components such as servers, storage, network devices,
virtualization software, and other storage resources that are needed to support the cloud computing
model.
7. Management
Management is used to manage components such as application, service, runtime cloud, storage,
infrastructure, and other security issues in the backend and establish coordination between them.
8. Security
Security is an in-built back end component of cloud computing. It implements a security
mechanism in the back end.
9. Internet

The Internet is medium through which front end and back end can interact and communicate with
each other.

Cloud Storage
Cloud Storage is a service that allows to save data on offsite storage system managed by third-
party and is made accessible by a web services API.
Cloud storage is a service model in which data is transmitted and stored on remote storage
systems, where it is maintained, managed, backed up and made available to users over a
network -- typically, the internet. Users generally pay for their cloud data storage on a per-
consumption, monthly rate.
Cloud storage is based on a virtualized storage infrastructure with accessible interfaces, near-
instant elasticity and scalability, multi-tenancy, and metered resources. Cloud-based data is
stored in logical pools across disparate, commodity storage servers located on premises or in a
data centre managed by a third-party cloud provider.
Cloud service providers manage and maintain data transferred to the cloud. Storage services
are provided on demand in the cloud, with capacity increasing and decreasing as needed.
Organizations opting for cloud storage eliminate the need to buy, manage and maintain in-
house storage infrastructure. Cloud storage has radically driven down the per-gigabyte cost of
storage, but cloud storage providers have added operating expenses that can make the
technology considerably more expensive, depending on how it's used.
Storage Devices
Storage devices can be broadly classified into two categories:
 Block Storage Devices
 File Storage Devices or Object Storage Devices
Block Storage Devices
 The block storage devices offer raw storage to the clients. These raw storages are
partitioned to create volumes.
 Block storage divides large volumes of data into smaller units called blocks. Each block
is associated with a unique identifier and placed on one of the system's storage drives.
Block storage is fast, efficient and provides the low latency required by applications
such as databases and high-performance workloads.
File Storage Devices
 The file Storage Devices offer storage to clients in the form of files, maintaining its
own file system. This storage is in the form of Network Attached Storage (NAS).
 File storage organizes data in a hierarchical system of files and folders; it is commonly
used with personal computer storage drives and network-attached storage (NAS). Data
in a file storage system is stored in files, and the files are stored in folders. Directories
and subdirectories are used to organize the folders and locate files and data. A file
storage-based cloud can make data access and retrieval easier, with this hierarchical
format being familiar to users and required by some applications.
 Object storage stores data as objects, which consist of three components: data stored in
a file, metadata associated with the data file and a unique identifier. Using the RESTful

API, an object storage protocol stores a file and its associated metadata as a single object
and assigns it an identification (ID) number. To retrieve content, the user presents the
ID to the system and the content is assembled with all its metadata, authentication and
security. Object-based storage systems allow metadata to be customized, which can
streamline data access and analysis. With object storage, data can be stored in its native
format with massive scalability.
Object storage (also known as object-based storage) is a computer data storage
architecture that manages data as objects, as opposed to other storage architectures like
file systems which manage data as a file hierarchy and block storage which manages
data as blocks within sectors and tracks. Each object typically includes the data itself,
a variable amount of metadata, and a globally unique identifier.
Object storage can be implemented at multiple levels, including the device level (object
storage device), the system level, and the interface level. In each case, object storage
seeks to enable capabilities not addressed by other storage architectures, like interfaces
that can be directly programmable by the application, a namespace that can span
multiple instances of physical hardware, and data management functions like data
replication and data distribution at object-level granularity. Object storage systems
allow retention of massive amounts of unstructured data.
Object storage is used for purposes such as storing photos on Facebook, songs on
Spotify, or files in online collaboration services, such as Dropbox. The majority of
cloud storage available in the market uses the object storage architecture. Two notable
examples are Amazon Web Services S3, which debuted in 2005, and Rackspace Files.
Other major cloud storage services include IBM Bluemix, Microsoft Azure, Google
Cloud Storage, Alibaba Cloud OSS, Oracle Elastic Storage Service and DreamHost
based on Ceph.
Characteristics of Object Storage
Advantages
Scalable capacity

Disadvantages
shells and
utility interfaces (POSIX
utilities) do not work directly with object-storage
-object basis than block storage
The Object Storage is suited for the following:
-structured data
The Object Storage is not suited for the following:
Cloud Storage Classes
Cloud storage can be broadly classified into two categories:
 Unmanaged Cloud Storage
 Managed Cloud Storage
Unmanaged Cloud Storage

Unmanaged cloud storage means the storage is preconfigured for the customer. The customer
can neither format, nor install his own file system or change drive properties.
Managed Cloud Storage
Managed cloud storage offers online storage space on-demand. The managed cloud storage
system appears to the user to be a raw disk that the user can partition and format.
Creating Cloud Storage System
The cloud storage system stores multiple copies of data on multiple servers, at multiple
locations. If one system fails, then it is required only to change the pointer to the location,
where the object is stored.
To aggregate the storage assets into cloud storage systems, the cloud provider can use storage
virtualization software known as Storage GRID. It creates a virtualization layer that fetches
storage from different storage devices into a single management system. It can also manage
data from CIFS and NFS file systems over the Internet. The following diagram shows how
Storage GRID virtualizes the storage into storage clouds:
Virtual Storage Containers
The virtual storage containers offer high performance cloud storage systems. Logical Unit
Number (LUN) of device, files and other objects are created in virtual storage containers.
Following diagram shows a virtual storage container, defining a cloud storage domain:

Challenges
Storing the data in cloud is not that simple task. Apart from its flexibility and convenience, it
also has several challenges faced by the customers. The customers must be able to:
 Get provision for additional storage on-demand.
 Know and restrict the physical location of the stored data.
 Verify how data was erased.
 Have access to a documented process for disposing of data storage hardware.
 Have administrator access control over data.
Benefits and considerations of using cloud services
Advantages:
 Pay as you go. With a cloud storage service, customers only pay for the storage they use,
eliminating the need for big capital expenses. While cloud storage costs are recurring,
rather than a one-time purchase, they are often so low that, even as an ongoing expense,
they may still be less than the cost of maintaining an in-house system.
 Utility billing. Because customers only pay for the capacity they use, cloud storage costs
can decrease as usage drops. This is in stark contrast to using an in-house storage system,
which will likely be over configured to handle anticipated growth. A company will pay for
more than it needs initially, and the cost of the storage will never decrease.

 Global availability. Cloud storage is typically available from any system, anywhere and
at any time; users do not have to worry about operating system (OS) capability or complex
allocation processes.
 Ease of use. Cloud storage is easy to access and use, so developers, software testers and
business users can get up and running quickly without having to wait for an IT (information
technology) team to allocate and configure storage resources.
 Off-site security. By its very nature, public cloud storage offers a way to move copies of
data to a remote site for backup and security purposes. Again, this represents a significant
cost savings when compared to a company maintaining its own remote facility.
An in-house cloud storage system can offer some of the above ease-of-use features of a public
cloud service, but it will lack much of the storage capacity flexibility of a public service. Some
hardware vendors are trying to address this issue by allowing their customers to turn on and
off capacity that has already been installed in their arrays.
Scalability, flexibility and multi-tenancy are all among the advantages of using cloud storage.
Cloud storage considerations

To determine whether using cloud storage will result in operational efficiencies and be cost-
effective, a company must take these four steps:
1. Compare the one-time and recurring costs of purchasing and managing storage capacity in-
house versus the ongoing costs of storing and accessing data in the cloud.
2. Determine if additional telecommunications expenses will be required for the appropriate
access to the service provider.
3. Decide if the cloud storage service provides adequate security and data governance.
4. Develop an in-house cloud security strategy, with procedures for access and use of cloud
storage to maintain effective management of data and control expenses.

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