Description
1.1 Definition & Characteristics
Cloud Computing is the on-demand delivery of IT resources (servers, storage, databases, networking, software) over the internet with pay-as-you-go pricing.
Key Characteristics:
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On-demand Self-service: Users can provision resources automatically without human intervention from the provider.
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Broad Network Access: Services are available over the network and accessed through standard mechanisms (mobile phones, tablets, laptops).
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Resource Pooling: The provider’s computing resources are pooled to serve multiple consumers (Multi-tenancy).
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Rapid Elasticity: Resources can be elastically provisioned and released to scale rapidly outward and inward with demand.
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Measured Service: Cloud systems automatically control and optimize resource use by leveraging a metering capability (Pay-per-use).
1.2 Cloud Deployment Models
| Model | Description | Advantages | Disadvantages |
| Public | Owned and operated by third-party cloud service providers (e.g., AWS, Azure). | Low cost (No hardware purchase), high scalability, no maintenance. | Lower security control, shared resources, less customization. |
| Private | Used exclusively by one organization; can be physically located on-site or hosted by a provider. | High security/privacy, total control, customizable. | Expensive (CapEx), requires IT expertise to maintain. |
| Community | Shared by several organizations with common concerns (e.g., hospitals, banks). | Cost-sharing among entities, better security than public. | Limited bandwidth/storage shared among many. |
| Hybrid | A combination of Public and Private clouds, allowing data/apps to be shared between them. | Ultimate flexibility, cost-efficiency, “Cloud Bursting” capability. | Complex to manage and integrate. |
1.3 Cloud Service Models
IaaS (Infrastructure as a Service)
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Function: Provides virtualized computing resources (Servers, VM, Storage) over the internet.
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Pros: Maximum flexibility, eliminates hardware costs.
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Cons: User is responsible for OS, apps, and data security.
PaaS (Platform as a Service)
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Function: Provides a framework for developers to build, test, and deploy applications.
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Pros: Streamlines workflows, reduces coding time for infrastructure.
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Cons: Vendor lock-in; limited to the provider’s tools.
SaaS (Software as a Service)
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Function: Delivers software applications over the internet via subscription.
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Pros: No installation needed, automatic updates, accessible anywhere.
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Cons: Dependent on internet connectivity, less control over data.
1.4 Cloud Cost Benefits
Transitioning to the cloud offers several financial advantages:
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CapEx to OpEx: Shifts “Capital Expenditure” (buying hardware) to “Operational Expenditure” (paying for what you use).
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Lower TCO: Reduces Total Cost of Ownership by eliminating electricity, cooling, and physical security costs.
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Economies of Scale: Large providers buy hardware in bulk, passing those savings to the user.
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Pay-as-you-go: You only pay for the minutes or gigabytes you actually consume.
1.5 Architectural & Infrastructural Components
If you need short keywords for quick recall, focus on these:
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Front-end: Client-side, User Interface (UI), Web Browser.
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Back-end: Servers, Storage, Runtime Environment, Security, Management.
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Middleware: Communication bridge between Front-end and Back-end.
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Hypervisor: Software that creates and runs Virtual Machines (VMs).
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Virtualization: The core technology that partitions physical hardware into multiple virtual elements.
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Service Level Agreement (SLA): The contract defining uptime and performance expectations.
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