Evolution of Cloud Computing

Today cloud represents a huge market one that is continuing to grow at an unprecedented scale enormous computational power once considered a prerogative of large enterprises is now available at the fingertips of even the smallest of businesses and individual developers thanks to the cloud moreover the cloud makes all this computational power highly affordable with pay as you go economics if you look at some of the key emerging technologies of our times such as artificial intelligence, the Internet of Things, blockchain and analytics all of these technologies work with massive amounts of data and need huge storage space and computational power to work making cloud possibly the only viable platform for these technologies.  

Cloud computing also referred to as the cloud is for the delivery of on-demand computing resources everything from applications to data centers over the Internet on a pay-for-use basis to get a common understanding of cloud computing. 

The U.S. (NIST)National Institute of Standards and Technology defines cloud computing as "A model for enabling convenient on-demand network access to a shared pool of configurable computing resources that can be rapidly provisioned and released with minimal management effort or service provider interaction", examples of computing resources include networks, servers, storage, applications, and services. 

This cloud model is composed of five essential characteristics, three deployment models, and three service models. The five essential characteristics of the cloud which include on Demand self-service(this characteristic means that you get access to cloud resources such as the processing power storage and network you need using a simple interface without requiring human interaction with each service provider), Broad Network access(this characteristic  means that cloud computing resources can be accessed via the network through standard mechanisms and platforms such as mobile phones tablets laptops and workstations), Resource pooling(this characteristic resource pooling is what gives cloud providers economies of scale which they pass on to their customers making cloud cost efficient using a multi-tenant model computing resources are pooled to serve multiple consumers cloud resources are dynamically assigned and reassigned according to demand without customers needing to concern themselves with the physical location of these resources) ,Rapid elasticities(this characteristic implies that you can access more resources when you need them and scale back when you don't because resources are elastically provisioned and released) and Measured service(this characteristic means that you only pay for what you use or reserve as you go if you're not using resources you're not paying resource usage is monitored, measured and reported transparently based on utilization).

Cloud computing is really about utilizing technology as a service leveraging remote systems on-demand over the open Internet scaling up scaling back and paying for what you use. It is a revolution in that it has changed the way the world consumes compute services by making them more cost-efficient while also making organizations more agile in responding to changes in their markets. 

There are three types of cloud deployment models Public(public cloud is when you leverage cloud services over the open Internet on hardware owned by the cloud provider but its usage is shared by other companies), Private(private cloud means that the cloud infrastructure is provisioned for exclusive use by a single organization it could run on-premises or it could be owned managed and operated by a service provider) and Hybrid(when you use a mix of both public and private clouds working together seamlessly that is classified as the hybrid model).  

The three service models that are based on the three layers in a computing stack infrastructure platform and applications these cloud computing models are referred to as Infrastructure as a service (IaaS), Platform as a service (PaaS), and software as a service (SaaS).In the infrastructure as a service model (IaaS), you get access to infrastructure and physical computing resources such as servers networking storage, and data center space without the need to manage or operate them. In a platform as a service (PaaS) model, you get access to the platform that is hardware and software tools usually those needed to develop and deploy applications to users over the Internet. Software as a service (SaaS) is a software licensing and delivery model in which software and applications are centrally hosted and licensed on a subscription basis and sometimes also referred to as on-demand software. 

Cloud computing is an evolution of technology over time, the concept of cloud computing dates to the 1950s when Large-scale mainframes with High-Volume processing power became available to make efficient use of the computing power of the mainframe. The practice of time-sharing, or resource pooling, evolved. Using dumb terminals, whose sole purpose was to facilitate access to the mainframes multiple users were able to access the same data storage layer and CPU power from any terminal. In the 1970s with the release of an operating system called virtual machine or VM, it became possible for mainframes to have multiple virtual systems, or virtual machines, on a single physical node. The virtual machine operating system evolved from the 1950s application of shared access, it's the mainframe by allowing multiple distinct computing environments to exist on the same physical hardware.

Each virtual machine hosted guest operating systems that behaved as though they had their memory, CPU, and hard drives, even though these were shared resources. Virtualization thus became a technology driver and a huge catalyst for some of the biggest evolutions in communications and computing, even 20 years ago physical hardware was quite expensive. With the Internet becoming more accessible and the need to make hardware costs more viable servers were virtualized into Sharing hosting environments, Virtual private servers, and Virtual dedicated servers using the same types of functionality provided by the virtual machine operating system. So for example, if a company needed 'X' number of physical systems to run their applications they could take one physical node and split it into multiple virtual systems, this was enabled by hypervisors. A hypervisor is a small software layer that enables multiple operating systems to run alongside each other sharing the same physical computing resources, a hypervisor also separates the virtual machines logically assigning each slice of the underlying computing power memory and storage preventing the virtual machines from interfering with each other. If for example, one operating system suffers a crash or a security compromise the others can keep working. 

As technologies and hypervisors improved and were able to share and deliver resources reliably some companies decided to make the benefits of the cloud accessible to users who didn't have an abundance of physical servers to create their cloud computing infrastructure. Since the servers were already online the process of spinning up a new instance was instantaneous. Users could now order cloud resources they needed from a larger pool of available resources and they could pay for them on a per-use basis also known as 'Pay-as-you-go'. This Pay-as-you-go or utility computing model became one of the key drivers behind cloud computing taking off. The Pay-as-you-go model allowed companies and even individual developers to pay for the computing resources as and when they used them just like units of electricity. 

This allowed them to switch to a more cash flow-friendly OpEx(Operating Expense - No or low up-front costs) model from a CapEx(Capital Expense – High up-front costs) model. This model appealed to all sizes of companies those who had little or no hardware and even those that had lots of hardware, because now instead of making huge capital expenditures and hardware they could pay for computing resources as and when needed it. Also, allowed them to scale their workloads during usage peaks and scale down when usage subsided and this gave rise to modern-day cloud computing the impact of the evolution of the cloud has been immense.