Cloud computing Unit2.pdf notes for bca II nd year

For bca

1. UNIT – 2
CLOUD SERVICE MODELS
Cloud computing is a model that enables the end users to access the shared pool of
resources such as compute, network, storage, database, and application as an on-demand
service without the need to buy or own it. The services are provided and managed by the service
provider, reducing the management effort from the end user side. There are three basic service
models, Infrastructure as a Service (IaaS), Platform as a Service (PaaS) and Software as a
Service (SaaS) as shown in figure.


Infrastructure as a Service (IaaS):
IaaS is also known as Hardware as a Service (HaaS). The ability given to the
infrastructure architects to deploy or run any software on the computing resources provided by
the service provider. Here, the infrastructures such as compute, network, and storage are
managed by the service provider. The end users are responsible for managing applications that
are running on top of the service provider cloud infrastructure. Generally, the IaaS services are
provided from the service provider cloud data center. The end users can access the services
from their devices through application programming interfaces (APIs) provided by the service
providers. The main advantage of using IaaS is that it helps users to avoid the cost and
complexity of purchasing and managing the physical servers.
Ex: Amazon web services, Google Compute Engine

Key Features of IaaS:
1. Virtualization: Hardware resources like servers and storage are virtualized and
delivered as services.
2. Pay-as-you-go: You only pay for what you use.
3. Scalability: Resources can be scaled up or down instantly as per demand.
4. Managed Infrastructure: Cloud providers handle hardware maintenance, power and
networking.
5. Flexibility: Users can install any operating system or software they need.

2. 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: Provides virtual networking components such as virtual router, switch, and
bridge for the VMs.
4. Load balancers: It provides load balancing capability at the infrastructure layer.


Advantages of IaaS:
1. Cost-Effective: No need to buy and Maintain expensive physical hardware (servers,
storage, networking).
2. 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.
3. Shared infrastructure: IaaS allows multiple users to share the same physical
infrastructure.
4. Global Accessibility: IaaS resources can be accessed from anywhere with an internet
connection.
5. Focus on the core business: IaaS providers focus on the organization's core business
rather than on IT infrastructure.
6. 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:
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. Internet Dependency: IaaS is completely dependent on a stable internet connection.
Any network outage can stop access to servers and applications.
4. Technical complexity: Users need technical expertise to manage virtual machines,
operating systems, and software configurations.
5. Limited control over physical hardware: Users can control virtual machines but dot
have access to physical servers.
Characteristics of IaaS:
1. On-Demand Resources: Provides computing resources (servers, storage, networking,
and virtualization) whenever required, without upfront investment.
2. Scalability & Elasticity: Users can scale infrastructure up or down quickly depending
on workload demands.

3. 3. Pay-As-You-Go Pricing: Costs are based on usage (CPU hours, storage space, network
bandwidth), reducing unnecessary spending.
4. Automated Administrative Tasks: Cloud providers handle hardware setup,
maintenance, backup, and disaster recovery.
5. Dynamic Resource Allocation: Resources can be automatically allocated or
reallocated in response to workload changes.
6. Accessible via Internet: Users can access infrastructure resources from anywhere
through secure internet connections.
Key Providers of IaaS:
o AWS EC2
o Google Compute Engine
o Azure VMs