Anyone who starts working with Microsoft Azure runs into words like cloud, public cloud, hybrid or "shared responsibility" within the first few minutes. This lesson clarifies the basic terms on which everything else in the course builds. You don't need any programming knowledge for it, only a basic understanding of IT terms such as server, storage and network.

What cloud computing is

Cloud computing is the delivery of computing services over the internet. These services include the usual IT infrastructure: virtual machines, storage, databases and networks. On top of that come services for the Internet of Things (IoT), for machine learning and for artificial intelligence.

Because the services come over the internet, you are not tied to a datacenter of your own. When you need to expand your IT equipment quickly, you don't wait for a new datacenter to be built, you use the cloud.

An example: The made-up company "Lindenhof Möbel" expects many visitors to its online shop at the start of a summer sale. Instead of buying and setting up additional servers months in advance, the team starts additional computing power in the cloud for the duration of the sale and shuts it down again afterwards. That way spending adapts to actual demand.

Shared responsibility

In a traditional datacenter that belongs to your company (on-premises), you are responsible for everything: for the room, the security, the servers, replacing them when they fail, the software and installing updates.

In the cloud, this responsibility is shared between the provider and you. This is called the shared responsibility model. The provider takes care of physical security, power supply, cooling and network connectivity. That makes sense: You don't sit in the datacenter, so you couldn't take care of those things anyway.

For some things, responsibility depends on the situation. If you use a database as a service from the provider, the provider maintains the database itself, but you remain responsible for the data that goes into it. If you instead install a database yourself on a virtual machine, you are also responsible for its updates and patches.

Responsibility is closely tied to the service types IaaS, PaaS and SaaS, which lesson 1.3 explains. With IaaS you carry the most responsibility, with SaaS the provider does, and PaaS lies in the middle.

Always with the provider Always with you Depends on the service type
the physical datacenter information and data in the cloud operating systems
the physical network devices that connect to your cloud (phones, computers) network controls
the physical hosts accounts and identities of people, services and devices applications
the infrastructure identity and access

On the topic of identity, a closer look is worthwhile: With PaaS and SaaS you manage your users, roles and policies yourself, while the provider runs the platform for sign-in, for example Microsoft Entra ID.

Public cloud, private cloud and hybrid cloud

The cloud models describe how cloud resources are provided.

Public cloud. An external provider builds, controls and maintains it. Anyone who wants to buy cloud services can use it. That is the key difference from the private cloud. Azure is an example.

Private cloud. A cloud environment that only a single organization uses. It grew out of the traditional datacenter. It can run in-house or in a datacenter of your own elsewhere, even at a third party. It offers more control, but costs more and brings fewer of the benefits of a public cloud.

Hybrid cloud. An environment that connects public and private cloud. With it you can, for example, extend a private cloud with public cloud resources when demand is temporarily higher. And you freely choose which services run in the public cloud and which stay in your private cloud.

Public cloud Private cloud Hybrid cloud
no investment needed to grow full control over resources and security the greatest flexibility
applications deployed quickly and removed again your data does not sit next to that of other tenants you decide where an application runs
you pay only for what you use hardware must be bought and maintained you control security, compliance and legal requirements
no complete control over resources and security you are responsible for maintenance and updates of the hardware

Two more terms belong here. With multicloud you use several public cloud providers, for example because you need certain features of another provider or are currently moving from one to the other. And Microsoft names two Azure offerings for mixed environments: Azure Arc helps you manage your environment, whether it runs only in Azure, as a private cloud in your own datacenter, as a hybrid or with several providers. Azure VMware Solution lets you run VMware workloads in Azure if you currently have a VMware environment in a private cloud.

Which model for what

  • Public cloud: You want to start quickly without buying hardware and pay only for what you use. Example: A young company tests a new app and needs servers for only a few weeks.
  • Private cloud: You need full control over resources and security and want your data not to sit next to that of others. In return you accept the costs and the maintenance effort.
  • Hybrid cloud: You want to decide yourself what runs where, or move demand peaks to the public cloud while sensitive services stay private. Anyone who already uses VMware in-house and wants to move step by step also finds their way here.

Back to "Lindenhof Möbel": The shop runs in the public cloud because the load fluctuates. The customer database stays in the company's own datacenter for the time being because management wants to control it there. The result is a hybrid cloud.

Exercise 1

The made-up property management company "Brandt & Söhne" has two projects. First, it wants to run a tenant app in the public cloud and use a database as a service from the provider there. Second, it wants to keep its accounting in a datacenter of its own, but add extra computing power from the cloud for the annual settlement.

a) With the database as a service, who is responsible for maintaining the database, and who for the data? b) Who is responsible for the physical datacenter of the tenant app? c) What is the cloud model of the second project called, and why?

Solution 1

a) The provider takes over operating the database. Brandt & Söhne remains responsible for the data that goes into it. Had the company installed the database itself on a virtual machine, it would also be responsible for patches and updates.

b) The provider, always. The physical datacenter, the physical network and the physical hosts lie with the provider in every model. For data, devices and accounts, on the other hand, Brandt & Söhne always remains responsible.

c) A hybrid cloud: The company's own datacenter corresponds to the private side, the additional computing power comes from the public cloud, and both sides work connected. The temporary extra demand at the annual settlement is exactly the case Microsoft gives as an example.

Further reading