The cloud is made up of servers in data centers worldwide. “On-Prem” data centers are moving to the cloud.
“The cloud” refers to servers accessed over the Internet and the software and databases running on those servers. Cloud servers are located in data centers all over the world. Using cloud computing, users and companies cannot manage physical servers or run software applications on their machines.
The cloud enables users to access duplicate files and applications from almost any device. The computing and storage occur on servers in a data center instead of locally on the user’s device. This is why users can log in to their Instagram account on a new phone after their old phone breaks and still find their old version in place, with all their photos, videos, and conversation history. It works the same way with cloud email providers like Gmail or Microsoft Office 365 and with cloud storage providers like Dropbox or Google Drive.
For businesses, switching to cloud computing removes some IT costs and overhead: for instance, they no longer need to update and maintain their servers, as the cloud vendor they are using will do that. This significantly impacts small businesses that may not have been able to afford their internal infrastructure but can outsource their infrastructure needs affordably via the cloud. The cloud can also make it easier for companies to operate internationally because employees and customers can access duplicate files and applications from anywhere.
How does cloud computing work?
Cloud computing is possible because of a technology called virtualization. Virtualization allows the creation of a simulated, digital-only “virtual” computer that behaves like a physical computer with its hardware. The technical term for such a computer is a virtual machine. When properly implemented, virtual machines on the same host machine are sandboxed from one another, so they do not interact with each other at all. The files and applications from one virtual machine are not visible to the other virtual machines even though they are on the same physical machine.
Virtual machines also make more efficient use of the hardware hosting them. By running many virtual machines at once, one server can run many virtual “servers,” A data center becomes like a whole host of data centers, able to serve many organizations. Thus, cloud providers can offer the use of their servers to far more customers at once than they would be able to otherwise, and they can do so at a low cost.
Even if individual servers go down, cloud servers should always be available online. Cloud vendors generally back up their services on multiple machines and across various regions.
Users access cloud services through a browser or an app, connecting to the cloud over the Internet — that is, through many interconnected networks — regardless of their device.
What are the primary service models of cloud computing?
Software-as-a-Service (SaaS): Instead of users installing an application on their device, SaaS applications are hosted on cloud servers, and users access them over the Internet. SaaS is like renting a house: the landlord maintains the place, but the tenant primarily uses it as if they owned it. Examples of SaaS applications include Salesforce, MailChimp, and Slack.
Platform-as-a-Service (PaaS): In this model, companies don’t pay for hosted applications; instead, they pay for the things they need to build their applications. PaaS vendors offer everything necessary for making an application, including development tools, infrastructure, and operating systems, over the Internet. PaaS can be compared to renting all the tools and equipment necessary for building a house instead of renting the home itself. PaaS examples include Heroku and Microsoft Azure.
Infrastructure-as-a-Service (IaaS): In this model, a company rents the servers and storage they need from a cloud provider. They then use that cloud infrastructure to build their applications. IaaS is like a company leasing a plot of land on which they can build whatever they want — but they must provide their building equipment and materials. IaaS providers include DigitalOcean, Google Compute Engine, and OpenStack.
Formerly, SaaS, PaaS, and IaaS were the three main models of cloud computing, and essentially all cloud services fit into one of these categories. However, in recent years a fourth model has emerged:
Function-as-a-Service (FaaS): FaaS, also known as serverless computing, breaks cloud applications down into smaller components that only run when needed. Imagine if it were possible to rent a house one little bit at a time: for instance, the tenant only pays for the dining room at dinner time, the bedroom while they are sleeping, the living room while they are watching TV, and when they are not using those rooms, they don’t have to pay rent on them.
FaaS or serverless applications, like all these cloud computing models, still run on servers. But they are called “serverless” because they do not run on dedicated machines, and the companies building the applications do not have to manage servers.
Also, serverless functions scale up, or duplicate, as more people use the application — imagine if the tenant’s dining room could expand on demand when more people come over for dinner!
What are the different types of cloud deployments?
In contrast to the models discussed above, which define how services are offered via the cloud, these different cloud deployment types have to do with where the cloud servers are and who manages them.
The most common cloud deployments are:
- Private cloud: A private cloud is a server, data center, or distributed network wholly dedicated to one organization.
- Public cloud: A public cloud is a service run by an external vendor that may include servers in one or multiple data centers. Unlike a private cloud, public clouds are shared by various organizations. Using virtual machines, different companies may share individual servers, a situation called “multitenancy” because multiple tenants rent server space within the same server.
- Hybrid cloud: hybrid cloud deployments combine public and private clouds and may include on-premises legacy servers. An organization may use its private cloud for some services and its public cloud for others, or it may use the public cloud as a backup for its private cloud.
- Multi-cloud: multi-cloud is a type of cloud deployment that involves using multiple public clouds. In other words, an organization with a multi-cloud deployment rents virtual servers and services from several external vendors — to continue the analogy used above, this is like leasing several adjacent plots of land from different landlords. Multi-cloud deployments can also be hybrid clouds and vice versa.
How is the cloud different from the traditional client-server model of the Internet?
The Internet has always consisted of servers, clients, and network infrastructure. Clients make requests to servers, and servers send responses. Cloud computing differs from this model in that cloud servers are not just responding to requests — they are running programs and storing data on the client’s behalf.
Why is it called ‘the cloud’?
“The cloud” started as a tech industry slang term. In the early days of the Internet, technical diagrams often represented the servers and networking infrastructure that comprise the Internet as a cloud. As more computing processes moved to this servers-and-infrastructure part of the Internet, people began to talk about moving to “the cloud” as a shorthand way of expressing where the computing processes were taking place. Today, “the cloud” is a widely accepted term for this style of computing.
What about containers? Are containers IaaS, PaaS, SaaS, or FaaS?
Like virtual machines, containers are a cloud virtualization technology. They are part of the PaaS (Platform-as-a-Service) cloud model. Virtualization for containers occurs one abstraction layer up from where it appears for virtual machines, at the operating system level instead of at the kernel level (the kernel is the foundation of the operating system, and it interacts with the computer’s hardware). Each virtual machine has its operating system kernel, but containers on the same machine share the same kernel.
