Cloud Computing Models & Services
Key Takeaways
- The three primary cloud service models are IaaS (Infrastructure — you manage OS and above), PaaS (Platform — you manage applications and data), and SaaS (Software — provider manages everything, you just use it).
- Public cloud resources are shared among multiple tenants (AWS, Azure, GCP), private cloud is dedicated to a single organization, and hybrid cloud combines both with data/apps moving between them.
- Cloud characteristics include on-demand self-service, broad network access, resource pooling, rapid elasticity (auto-scaling), and measured service (pay-per-use billing).
- Metered utilization means you pay only for the resources you use — ingress (data uploaded to cloud) is typically free, while egress (data downloaded from cloud) is charged.
- Cloud storage synchronization services (OneDrive, Google Drive, Dropbox, iCloud) keep files automatically synced across multiple devices, enabling seamless work from anywhere.
Last updated: March 2026
Cloud Computing Models & Services
Cloud Service Models
The three cloud service models define who manages what in the cloud:
Responsibility Comparison
| Component | On-Premises | IaaS | PaaS | SaaS |
|---|---|---|---|---|
| Applications | You | You | You | Provider |
| Data | You | You | You | Provider |
| Runtime | You | You | Provider | Provider |
| Middleware | You | You | Provider | Provider |
| OS | You | You | Provider | Provider |
| Virtualization | You | Provider | Provider | Provider |
| Servers | You | Provider | Provider | Provider |
| Storage | You | Provider | Provider | Provider |
| Networking | You | Provider | Provider | Provider |
IaaS (Infrastructure as a Service)
- You manage: Operating system, applications, data, runtime
- Provider manages: Physical hardware, networking, storage, virtualization
- Examples: Amazon EC2, Microsoft Azure VMs, Google Compute Engine, DigitalOcean
- Use Case: Running custom servers, legacy applications, full OS control
PaaS (Platform as a Service)
- You manage: Applications and data only
- Provider manages: Everything else (OS, runtime, middleware, infrastructure)
- Examples: Heroku, Google App Engine, Azure App Service, AWS Elastic Beanstalk
- Use Case: Developing and deploying applications without managing infrastructure
SaaS (Software as a Service)
- You manage: Nothing (just use the software)
- Provider manages: Everything
- Examples: Microsoft 365, Google Workspace, Salesforce, Dropbox, Zoom
- Use Case: End-user applications accessed via web browser
Memory Aid: Think of pizza analogy — IaaS = you cook at home with delivered ingredients, PaaS = you bring your own toppings to a prepared kitchen, SaaS = you order delivery pizza (fully ready).
Cloud Deployment Models
| Model | Description | Use Case |
|---|---|---|
| Public Cloud | Resources shared among multiple customers (multi-tenant) | Startups, general workloads, cost-sensitive projects |
| Private Cloud | Dedicated infrastructure for a single organization | Government, healthcare, financial services (regulatory compliance) |
| Hybrid Cloud | Combination of public and private with data/apps moving between them | Most enterprises — keep sensitive data private, use public for scalable workloads |
| Community Cloud | Shared by organizations with common requirements | Healthcare consortiums, government agencies, research groups |
Cloud Characteristics (NIST Definition)
| Characteristic | Description |
|---|---|
| On-Demand Self-Service | Users can provision resources without human interaction with the provider |
| Broad Network Access | Resources accessible from any device over standard networks (internet) |
| Resource Pooling | Provider's resources are shared among multiple customers (multi-tenancy) |
| Rapid Elasticity | Resources can automatically scale up or down based on demand |
| Measured Service | Resource usage is monitored, metered, and billed (pay-per-use) |
Cloud Metering and Billing
| Concept | Description |
|---|---|
| Metered Utilization | Pay only for what you use (CPU hours, storage GB, bandwidth) |
| Ingress | Data uploaded TO the cloud (usually free) |
| Egress | Data downloaded FROM the cloud (usually charged) |
| Reserved Instances | Pre-pay for long-term use at discounted rates |
| Spot/Preemptible | Use spare capacity at deep discounts (can be interrupted) |
Common Cloud Services
Cloud Storage & Sync
| Service | Provider | Integration |
|---|---|---|
| OneDrive | Microsoft | Windows, Microsoft 365 |
| Google Drive | Android, Google Workspace | |
| iCloud | Apple | macOS, iOS |
| Dropbox | Dropbox | Cross-platform |
Virtual Desktop Infrastructure (VDI)
- Full desktop environments hosted in the cloud
- Users access via thin clients, web browsers, or apps
- Examples: Amazon WorkSpaces, Azure Virtual Desktop, Citrix DaaS
- Benefits: Centralized management, security, BYOD support
Cloud-Based Email
- Microsoft 365 (Exchange Online)
- Google Workspace (Gmail)
- Benefits: No on-premises mail server, automatic updates, mobile access, spam filtering
Test Your Knowledge
A company uses Microsoft 365 for email and document editing. Which cloud service model is this?
A
B
C
D
Test Your Knowledge
Which cloud deployment model combines both public and private cloud resources?
A
B
C
D
Test Your KnowledgeMatching
Match each cloud service model to its example:
Match each item on the left with the correct item on the right
1
IaaS
2
PaaS
3
SaaS
4
Private Cloud
Test Your Knowledge
In cloud computing billing, what is the term for data downloaded FROM the cloud?
A
B
C
D