IT FundamentalsA+

Cloud Computing Concepts for CompTIA A+ 220-1101

Cloud computing delivers computing resources — servers, storage, databases, networking, software — over the internet on a pay-as-you-go basis. CompTIA A+ 220-1101 tests cloud service models (IaaS, PaaS, SaaS), deployment models (public, private, hybrid, community), and characteristics like shared resources and rapid elasticity. Understanding cloud fundamentals helps technicians support users working with cloud-based services.

7 min

2 sections · 7 exam key points

1 practice questions

Cloud Service Models

IaaS (Infrastructure as a Service): cloud provider delivers virtual hardware — servers (VMs), storage, networking. Customer manages: OS, middleware, runtime, applications, data. Customer has most control. Examples: AWS EC2, Microsoft Azure Virtual Machines, Google Compute Engine. Use case: replacing on-premises servers with cloud VMs.

PaaS (Platform as a Service): cloud provider delivers hardware + OS + middleware + runtime. Customer manages: applications and data only. Less administrative overhead. Examples: Google App Engine, Microsoft Azure App Service, Heroku. Use case: developers deploy applications without managing server OS.

SaaS (Software as a Service): cloud provider delivers the complete application. Customer just uses the software through a browser or app — manages only their data. Examples: Microsoft 365 (Office apps + Exchange + Teams), Google Workspace, Salesforce, Dropbox. Most end users interact with SaaS daily without realizing it. No installation required (web-based) — access from any device.

Shared responsibility model: in IaaS, the customer is responsible for securing the OS, applications, and data; the cloud provider secures physical infrastructure. In SaaS, the customer is responsible only for access management and data; the provider handles everything else. Understanding the boundary of responsibility is critical for security planning.

Cloud Deployment Models and Characteristics

Public cloud: owned and operated by a third-party provider (AWS, Azure, Google Cloud) — shared infrastructure, multiple customers (multi-tenant). Resources available on demand, pay-per-use, no upfront hardware investment. Most common for general workloads.

Private cloud: cloud infrastructure dedicated to one organization — can be on-premises (owned data center using cloud management software like VMware vSphere) or hosted exclusively by a provider. Higher security and compliance control. More expensive than public cloud.

Hybrid cloud: combination of public and private cloud connected to share data and applications. Organizations keep sensitive data private, use public cloud for burst capacity or less-sensitive workloads. Most enterprises use hybrid cloud.

Community cloud: shared by several organizations with common requirements (government agencies, healthcare organizations) — costs distributed among members. Less common than the other three models.

Key cloud characteristics (NIST definition): on-demand self-service (provision resources without human interaction with provider), broad network access (accessible from any device/location), resource pooling (multi-tenant infrastructure), rapid elasticity (scale up/down quickly), measured service (pay only for what you use). Metered service enables cost control — no capital expenditure.

Cloud Service Models: What You Manage

Layer	IaaS	PaaS	SaaS
Applications	Customer	Customer	Provider
Data	Customer	Customer	Customer
Runtime/Middleware	Customer	Provider	Provider
Operating System	Customer	Provider	Provider
Virtualization	Provider	Provider	Provider
Physical Servers	Provider	Provider	Provider

Key exam facts — A+

IaaS: virtual hardware (AWS EC2); PaaS: platform for app deployment (Heroku); SaaS: complete app (Office 365)
Public: multi-tenant, pay-as-you-go; Private: dedicated, more control; Hybrid: both
SaaS: customer manages only data and access — provider manages everything else
Five NIST cloud characteristics: on-demand, broad access, resource pooling, rapid elasticity, measured service
Metered service: pay only for what you use — no capital expense
Shared responsibility: IaaS = customer manages OS up; SaaS = customer manages data only
Hybrid cloud: most common enterprise model — sensitive data private, burst workloads public

Common exam traps

SaaS means the customer has no security responsibility

SaaS customers are still responsible for: managing user accounts and access permissions, controlling who can access the SaaS application, protecting their data within the SaaS system, and configuring sharing/privacy settings. The SaaS provider is responsible for the underlying infrastructure, application security, and availability — but data governance remains the customer's responsibility

Practice questions — Cloud Computing

These questions are representative of what you will see on A+ exams. The correct answer and explanation are shown immediately below each question.

Q1.A small business subscribes to Microsoft 365 for email and office applications. The IT staff does not manage any servers or operating systems for this service. Which cloud service model are they using?

A.IaaS (Infrastructure as a Service)

B.PaaS (Platform as a Service)

C.SaaS (Software as a Service)

D.Private cloud

Explanation: Microsoft 365 is SaaS — Microsoft manages everything: the physical servers, virtualization, operating systems, middleware, and the Office/Exchange/Teams applications themselves. The customer only manages their user accounts, licenses, data, and access policies. There is no server administration required. This is the defining characteristic of SaaS: the complete application is delivered as a service with minimal management responsibility on the customer side.

Frequently asked questions — Cloud Computing

What is the difference between cloud storage and cloud backup?

Cloud storage (Dropbox, Google Drive, OneDrive): synchronizes files to the cloud for access from multiple devices — primarily for availability and sharing. Deleting a file on one device syncs the deletion to all devices and the cloud. Cloud backup (Backblaze, Acronis, Carbonite): creates an independent, time-stamped archive of data — accidental deletions can be recovered because backup versions are retained according to policy. For data protection, use both: cloud storage for access and sharing, cloud backup for recovery from accidental deletion or disaster.

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