This book aims to take you on a journey along the different major cloud platforms and will try to answer one crucial question: if my organization deploys IT systems on various cloud platforms, how do I keep control? We want to avoid cases where costs in multi-cloud environments grow over our heads, where we don't have a clear overview of who's managing the systems, and, most importantly, where system sprawl introduces severe security risks. But before we start our deep dive, we need to agree on a common understanding of multi-cloud and multi-cloud concepts.

There are multiple definitions of multi-cloud, but we're using the one stated on https://www.techopedia.com/definition/33511/multi-cloud-strategy:

Multi-cloud refers to the use of two or more cloud computing systems at the same time. The deployment might use public clouds, private clouds, or some combination of the two. Multi-cloud deployments aim to offer redundancy in case of hardware/software failures and avoid vendor lock-in.

Let's focus on some topics in that definition. First of all, we need to realize where most organizations come from: traditional data centers with physical and virtual systems, hosting a variety of functions and business applications. If you want to call this legacy, that's OK. But do realize that the cutting edge of today is the legacy of tomorrow. Hence, in this book, we will refer to "traditional" IT when we're discussing the traditional systems, typically hosted in physical, privately owned data centers. And with that, we've already introduced the first problem in the definition that we just gave for multi-cloud.

A lot of enterprises call their virtualized environments private clouds, whether these are hosted in external data centers or in self-owned, on-premises data centers. What they usually mean is that these environments host several business units that get billed for consumption on a centrally managed platform. You can have long debates on whether this is really using the cloud, but the fact is that there is a broad description that sort of fits the concept of private clouds.

Of course, when talking about the cloud, most of us will think of the major public cloud offerings that we have today: AWS, Microsoft Azure, and GCP. By another definition, multi-cloud is a best-of-breed solution from these different platforms, creating added value for the business in combination with this solution and/or service. So, using the cloud can mean either a combination of solutions and services in the public cloud, or combined with private cloud solutions.

But the simple feature of combining solutions and services from different cloud providers and/or private clouds does not make up the multi-cloud concept alone. There's more to it.

Maybe the best way to explain this is by using the analogy of the smartphone. Let's assume you are buying a new phone. You take it out of the box and switch it on. Now, what can you do with that phone? First of all, if there's no subscription with a telecom provider attached to the phone, the user will discover that the functionality of the device is probably very limited. There will be no connection from the phone to the outside world, at least not on a mobile network. An option would be to connect it through a Wi-Fi device, if Wi-Fi is available. In short, one of the first actions, in order to actually use the phone, would be making sure that it has connectivity.

Now we have a brand new smartphone set to its factory defaults and we have it connected to the outside world. Ready to go? Probably not. The user probably wants to have all sorts of services delivered to their phone, usually through the use of apps, delivered through online catalogs such as an app store. The apps themselves come from different providers and companies including banks and retailers, and might even be coded in different languages. Yet, by compiling the apps – transforming the code in such a way that it can be read and understood by different devices – they will work on different phones with different versions of mobile operating systems such as iOS or Android.

The user will also very likely want to configure these apps to their personal needs and wishes. Lastly, the user needs to be able to access the data on their phone. All in all, the phone has turned into a landing platform for all sorts of personalized services and data.

The best part is that in principle, the user of the phone doesn't have to worry about updates. Every now and then the operating system will automatically be updated and most of the installed apps will still work perfectly. It might take a day or two for some apps to adapt to the new settings, but in the end, they will work. And the data that is stored on the phone or accessed via some cloud directory will also still be available. The whole ecosystem around that smartphone is designed in such a way that from the end user's perspective, the technology is completely transparent:

Figure 1.1 – Analogy of the smartphone—a true multi-cloud concept

Well, this is the cloud concept, where the smartphone in our analogy is the actual integrated landing zone, where literally everything comes together, providing a seamless user experience.