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A+ Core 1 · CompTIA 220-1201 V15 · Objective 4.1

Summarize cloud computing concepts

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Objective 4.1: Summarize cloud computing concepts

Cert: CompTIA A+ Core 1 (220-1201) V15 Domain: 4.0 Virtualization and Cloud Computing Weight: ~11% of Core 1 Depth: Summarize. Recognize cloud deployment models, service models, and core characteristics.

What this objective tests

You should be able to describe the four common cloud deployment models (private, public, hybrid, community), the three service models (IaaS, PaaS, SaaS), and the key characteristics of cloud computing (shared vs dedicated resources, metered utilization including ingress/egress, elasticity, availability, file synchronization, multitenancy).

Key facts

Cloud deployment models:

  • Private cloud. Cloud infrastructure operated solely for one organization. Either on-premises in the organization's own data center or hosted by a provider but dedicated to that customer. More control, more cost.
  • Public cloud. Multi-tenant cloud operated by a provider for many customers. AWS, Azure, Google Cloud, OCI. Lower cost, shared infrastructure.
  • Hybrid cloud. A mix of private and public cloud, with workloads moving between them based on requirements. A common SMB pattern: production on-prem, development and burst capacity in public cloud.
  • Community cloud. Shared cloud serving a specific industry or community (e.g., government cloud for federal agencies, healthcare-focused cloud for HIPAA-regulated providers).

Cloud service models:

  • IaaS (Infrastructure as a Service). The provider supplies the virtualized hardware: compute, storage, network. The customer manages everything above that (OS, middleware, applications). Examples: AWS EC2, Azure Virtual Machines.
  • PaaS (Platform as a Service). The provider supplies the runtime environment: OS, runtime, sometimes a managed database. The customer brings the application code. Examples: AWS Elastic Beanstalk, Azure App Service, Google App Engine.
  • SaaS (Software as a Service). The provider supplies the complete application, typically over the web. The customer just uses it. Examples: Microsoft 365, Google Workspace, Salesforce, Dropbox.

The shorthand: IaaS is "I rent the hardware." PaaS is "I rent the platform." SaaS is "I rent the application."

Cloud characteristics:

  • Shared vs dedicated resources. Public cloud is shared by many tenants. Some workloads can pay extra for dedicated hosts where their workloads are not co-located with others (security, compliance, or noisy-neighbor concerns).
  • Metered utilization. Cloud bills by consumption: compute hours, storage GB, network transfer.
  • Ingress and egress. Ingress (data coming into the cloud) is usually free. Egress (data leaving the cloud) is usually charged. Large data outflows from cloud back to on-prem can be expensive.
  • Elasticity. Resources scale up and down with demand. A web app can spin up extra servers during a traffic spike and release them afterward.
  • Availability. Most cloud providers offer SLAs measured in 9s (99.9%, 99.99%). Higher availability requires multi-region or multi-zone architectures.
  • File synchronization. Common cloud feature where files sync from a local device to the cloud and across the user's other devices. OneDrive, Google Drive, Dropbox, iCloud Drive.
  • Multitenancy. A single instance of a cloud service serves multiple tenants (customers) with logical separation. Cost-efficient for the provider; requires strong isolation to keep tenants from seeing each other's data.

Common gotchas

  • Confusing PaaS and IaaS. A managed Azure SQL Database is PaaS (provider runs SQL Server). A self-installed SQL Server on an Azure VM is IaaS (customer runs SQL Server on rented hardware).
  • Egress charge surprises. Customers download multiple terabytes from cloud storage and get a large bill. Read egress pricing before designing data flows.
  • 'Cloud' as a noun. Cloud is a deployment and consumption model, not a place. "Putting it in the cloud" still means it runs on real hardware somewhere, just not in the customer's data center.
  • Private cloud is not just on-prem virtualization. Private cloud requires self-service provisioning, elasticity, and metered consumption to qualify, not just a VMware cluster.
  • Hybrid cloud needs integration. Just having both on-prem and public cloud workloads is not hybrid; hybrid implies coordinated identity, networking, and workload mobility between the two.
  • Multitenancy and noisy neighbors. A loud tenant on shared hardware can affect another tenant's performance even though data is isolated. Dedicated hosts are one mitigation.

Real-world context

For SMB Revtek customers, the dominant pattern is:

  • SaaS for productivity. Microsoft 365 or Google Workspace.
  • SaaS for line-of-business apps. Industry-specific tools as a service rather than self-hosted.
  • IaaS or PaaS only when SaaS doesn't fit. Custom applications or legacy workloads.
  • Private cloud is rare for SMB. Cost and operational overhead outweigh benefits for most.

For Claire (the SMB persona):

  • Microsoft 365 (SaaS) is almost always the right answer for email, files, and productivity.
  • Backup-as-a-service (BaaS) provides offsite backup without on-prem infrastructure.
  • Hybrid is most relevant when she has an on-prem line-of-business app that can't move yet, but she wants new workloads in cloud.

Common helpdesk and consultation calls:

  • "Where are our files actually stored?" In the public cloud provider's data center, with some local caching depending on sync settings.
  • "Why did our cloud bill spike?" Egress charges, runaway compute, or a misconfigured service that ran 24/7 when it should have shut off.
  • "Can we keep everything on-prem?" Possible but usually more expensive and lower-availability than SaaS equivalents for SMB workloads.

Sources

  • [CompTIA A+ 220-1201 Exam Objectives Version 4.0, Section 4.2](../../../../../../30-RevyTechJourney/CompTIA%20A%2B%20220-1201%20Exam%20Objectives%20%284.0%29.pdf)
  • [NIST SP 800-145: The NIST Definition of Cloud Computing](https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-145.pdf)
  • [Wikipedia: Cloud computing](https://en.wikipedia.org/wiki/Cloud_computing)
  • [Wikipedia: Infrastructure as a service](https://en.wikipedia.org/wiki/Infrastructure_as_a_service)
  • [Wikipedia: Platform as a service](https://en.wikipedia.org/wiki/Platform_as_a_service)
  • [Wikipedia: Software as a service](https://en.wikipedia.org/wiki/Software_as_a_service)
  • [Microsoft Learn: Cloud computing types](https://learn.microsoft.com/en-us/azure/cloud-adoption-framework/migrate/azure-best-practices/cloud-models)