A to Z of the Cloud: Part three

Welcome to the third instalment of our A to Z series, explaining the wide world of cloud computing.

In our final instalment of this three-part A to Z series of terms you might commonly hear associated with the Cloud, we will take you through the letters S to Z. Our previous instalments have included a wide range of terms, from DevOps and Elastic computing to Operating system and Redundancy, and if you’d like to go back through and see the terms we have covered off already, you can read Part 1 here, and Part 2 here.  With just a few more terms left to explain for you, we now pick up where we left off with the letter S.  

S is for SaaS

Software as a Service, sometimes referred to as “on-demand software”, is a type of software which is hosted centrally “in the cloud” and paid for using a subscription, a so-called pay-as-you-go model. Users can access the services via any internet enabled device with a web browser and as a bulk of the processing occurs in the cloud, the end-users do not need high-end equipment.

SaaS is considered to be part of the nomenclature of cloud computing along with “Infrastructure as a Service” (IaaS), “Platform as a Service” (PaaS); the differentiator being that SaaS is designed for the end-user. Examples of SaaS applications include email and collaboration software, customer relationship management software and accountancy services. It represents the largest sub-section of the cloud market and it is growing fast.

T is for Topology

Topology in networking refers to the way in which constituent nodes are logically or physically arranged and is a major consideration when designing computer networks. Simple examples of topological structures are bus networks, where each node is connected to a single cable, or mesh networks, where each node relays data and all mesh nodes cooperate in the distribution of data in the network.

At large scales, for instance when talking about the network topologies used in cloud data centres, more complicated models such as Jellyfish topologies are used; this is where core nodes are closely linked but the tentacle nodes are less tightly bound. A jellyfish topology gives a good balance between redundancy, speed and complexity.

U is for Utility computing

Utility computing is often lumped together with the broad concept of cloud computing, but the term refers specifically to paying only for what you use, just as you do with utilities such as electricity or water. The key advantage to businesses using this type of subscription model for payment is that they do not have an initial up-front cost, therefore avoiding large capital expenditures associated with purchasing computer equipment or investing in data centres.

The utility in question could be compute, as in the IaaS model, or it could be something else such as storage where you pay based on storage capacity used.

Utility computing is often lauded as one of the biggest benefits of the cloud computing model.

V is for Virtual Machine

A virtual machine, or VM, is a software computer which emulates a dedicated computer system. This means that functions of computer hardware are emulated in software, providing virtual hardware including a virtual CPU, memory, hard drive, network interface and other devices. The software in the virtual machine then maps these virtual devices to real hardware on a physical machine.

The virtual machine can run an operating system as well as applications, just like a physical computer and multiple VMs can run on one physical computer by using VM-management software called a hypervisor. In IaaS, the infrastructure provided as a service is often in the form of a virtual machine.

W is for Waterfall methodologies

The waterfall methodology is a traditional software development model which uses a sequential design process. In this sequential model, progress is seen as flowing downwards, in a stepped process, similar to a waterfall.

The waterfall method begins with gathering requirements, then moves onto design, followed by the main development process and finally moves onto testing and implementation. Each new version or new feature that is rolled out in the application follows the same sequential process. It is still a dominant process model in software development although many companies have moved towards methods more aligned with the field of DevOps such as Agile.

X is for Xen Project

The Xen Project is part of The Linux Foundation and is home for several virtualisation-related open source projects including the Xen Hypervisor which is the open source standard for hardware virtualisation. Designed for the Linux and BSD operating systems, the Xen Hypervisor allows multiple computer operating systems to be hosted and run simultaneously on the same computer hardware. Xen software underpins many cloud providers, including Amazon Web Services (AWS) and Aliyun, the Alibaba Cloud.

Y is for Yottabyte

The Yottabyte is a storage unit for digital information, it refers to the eighth power of 1000 or 10^24 bytes and is the largest storage unit defined in the International System of Units. Its name is derived from the Ancient Greek okto, meaning eight. A Yottabyte of digital information has never been stored but it has been estimated that the world’s internet traffic would surpass one Zettabyte in 2016 and another estimate calculated that if all human speech ever spoken was digitised it would amount to 42 Zettabytes - a Yottabyte consists of 1024 Zettabytes.

Z is for Zones

Zones, or availability zones, are isolated geographic locations within data centre regions from which public cloud services originate and operate. Examples may include “Asia-Pacific”, “South America” or “European Union”; some providers allow for availability zones limited to a single city within a region. Businesses select one or more availability zones to use when setting up their cloud computing services in order to choose where their services are located.

An availability zone can hold one or more data centres and each availability zone is designed to be isolated from failures in other zones; this means that deploying an application across zones gives some measure of resiliency. Choosing a local availability zone gives advantages such as lower latency and helps meet data sovereignty requirements.

Tony Connor, Head of EMEA Marketing, Datapipe
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