Comparing the cloud computing service models

Each service model has its characteristics. The most appropriate model is defined by how much you want (or need/mandate) to control, secure, and manage your resources, for example, your apps, code, data, networks, security, and so on. From the last section, we can now define what the service models are; this section looks at the characteristics of each model in more detail to help you understand when you may choose one service model over the other.

Characteristics of IaaS

In a nutshell, IaaS is a model where you can host your virtual machines and infrastructure services on hardware provided for you and shared with other tenants.

The cloud provider is responsible for providing all layers up to and including the hardware; you are responsible for providing all layers preceding (refer to Figure 1.10).

The following are the characteristics of IaaS:

  • You create the virtual machine (install an OS and software), storage, and computing resources as you would in a traditional on-premises computing model; this can be likened to a virtual data center. There is the ability to provide fault tolerance, redundancy through availability solutions in case of failure within an Azure data center, zone, or region.
  • You have control to increase resources such as the processor, memory, and storage of a virtual machine by using self-service without requiring to redeploy or create a new virtual machine of the required spec.
  • Based on the OpEx model, meaning you only pay for resources you consume on a pay-as-you-go basis; you only pay for a virtual machine while it’s running, therefore your month-to-month running charges may be different across virtual machines if you run them for a different number of hours in the month. You will not be charged while it is in the stopped deallocated state; storage costs will still be charged if you wish to persist the data on disks.
  • It provides the greatest control and flexibility to deploy, configure, manage, and support resources as you require and requires the most management and administrative and operations overhead.
  • You have direct access and complete control of the virtual machine, the operating system, and any roles/services such as the web server, application server, or SQL server that may be required to be installed/running on the virtual machines, as well as complete control over decisions on networking, security, and protection.

The following are examples of Microsoft IaaS resources:

  • Azure Virtual Machines
  • Azure Storage
  • Azure Networking

Characteristics of PaaS

In a nutshell, PaaS is a model where you host your application, code, data, and business logic on compute, and storage resources are provided for you and shared with other tenants, but secured and isolated from other tenants.

The cloud provider is responsible for providing all layers up to and including the compute; you are responsible for providing all layers above (refer to Figure 1.10).

The following are the characteristics of PaaS:

  • It provides a ready-to-use environment and platform for faster deployment of hosting web applications, code, business logic, data, and so on. Using pre-deployed resources, development frameworks, languages, and runtimes provided as a service, there is a quicker time to value and consumption of the service.
  • It provides on-demand autoscaling of the platform used by a hosted application and services.
  • You have control to increase resources by changing the pricing tier of the service by using self-service; you must still select underlying compute resources sizing to host your app, code, and so on.
  • You would have no direct access or control of the virtual machine or any applications, services, or roles that may be installed; you do not get to specify or control which versions are available.
  • Because the service provider is responsible for the compute and storage resources layer, it gives you the least control and least flexibility. Still, it requires the least amount of management, administrative, and operations overhead.

The following are examples of Microsoft PaaS services:

  • Azure App Service
  • Azure SQL Database
  • Cosmos DB
  • Azure Files
  • Azure Active Directory Domain Services (AADDS)

Characteristics of FaaS (serverless)

In a nutshell, FaaS is a model where you provide your code and business logic and the cloud provider hosts it in their language, runtime, and compute environment shared with other tenants.

The cloud provider is responsible for providing all layers up to and including the language, runtime, and compute. You are responsible for providing all layers above, that is, the business logic layer (refer to Figure 1.10).

The following are the characteristics of FaaS:

  • Azure Functions is a serverless code engine. It has the use case of events that trigger code; that is, Functions code being executed is a response or action based on an event trigger.
  • Azure Logic Apps is a serverless workflow engine. It has the use case of events that trigger workflows; that is, a Logic Apps workflow is a response or action based on an event trigger.
  • You only have control over your application, code, and business logic layer; all other layers are provided as a service that you have no access or control over. Essentially, you take the layers supplied to you and use that to execute (run/launch) your code/workflow. Using the pizza analogy covered earlier, this is much like what could be described as a take and bake approach; ultimately, you are still responsible for cooking, but they have provided all the layers below, so it’s ready to cook, as it were, much like a microwave meal, or taking the packaging off a pizza and putting it straight in the oven.
  • It provides the least control and flexibility but abstracts all the layers below, providing the least amount of deployment, configuration, and maintenance, so you can focus on the application, code, and business logic layers, where the value is, without needing to concern yourself with the layers below.

The following are examples of Microsoft Serverless resources:

  • Azure Functions
  • Azure Logic Apps

Characteristics of SaaS

In a nutshell, SaaS is a model where you consume an application provided for you and shared with other tenants.

The cloud provider is responsible for providing all the layers up to and including the applications; you are not responsible for any layers above other than the configuration and consumption of the app (refer to Figure 1.10).

The following are the characteristics of SaaS:

  • The cloud provider installs the application/solution and is responsible for its updates, scalability, availability, and security.
  • It provides the greatest time to value as there is no development time or resources required to create an application; it can be directly configured as needed and used instantly.
  • In our pizza analogy, all the layers are taken care of for us, so all we need to do is just eat; this is the classic takeaway approach.
  • It provides the minimum amount of control and input on the lower layers.

The following are examples of Microsoft SaaS solutions:

  • Microsoft Teams
  • Microsoft Exchange Online
  • Microsoft SharePoint Online
  • Microsoft OneDrive
  • Microsoft Dynamics 365

The following are examples of other vendors’ SaaS solutions:

  • Zoom
  • Salesforce
  • Dropbox
  • Google Mail/Google Docs

In this section, we covered the service models of IaaS, PaaS, and SaaS and introduced the concept of serverless computing as an extension of PaaS. We compared and contrasted each service model and outlined the characteristics unique to a particular model and those common across the models.