A public cloud is a cloud computing model based on jointly used physical hardware, which belongs to and is operated by a third party provider. The entire infrastructure is located at a cloud computing company, which offers the cloud service. The location is separated from the customer, who has no physical control over the infrastructure. The infrastructure of a public cloud is jointly used by many customers. Google Cloud, Amazon Web Services and Microsoft Azure are examples for public clouds. Some of the most common applications for public cloud services include cloud-based server hosting, webmail, backup services and online Office applications.
Services of a Public Cloud
Public cloud service providers offer customers different cloud computing models, which are referred to as IaaS, PaaS and SaaS.
IaaS – Infrastructure-as-a-Service
Infrastructure-as-a-Service is the lowest layer in cloud computing and refers to a cloud-based infrastructure as a completely outsourced service. An IaaS provider provides pre-installed and configured hardware or software via a virtualised interface. How customers, who use the service, access cloud services is up to them. Examples for IaaS offers are managed hosting and development environments. The most important providers of Infrastructure-as-a-Service solutions include Google, IBM, Rackspace Cloud-Server, Amazon EC2 and Verizon. IaaS solutions reduce overall operating costs and investments as users only pay for those services, which they actually use. Users are able to scale IaaS services at any time depend on their requirements.
PaaS – Platform-as-a-Service
This type of cloud computing resembles IaaS but is more advanced. With Platform-as-a-Service providers not only offer an infrastructure, but also a platform and a solution stack as a service. The IT infrastructure can be equipped with a graphical user interface, run time system libraries, programming languages or an operating system. PaaS services are mainly used by companies who have to develop, test and provide cloud solutions for certain applications. However, the hosting of the application is implemented by a third party – the PaaS provider. PaaS providers offer a completely configured sandbox and implementation environment, in which customers can develop, test and provide cloud applications.
Platform-as-a-Service providers are for example Salesforce.com, Force.com, Rackspace Cloud-Sites, Google App Engine and Microsoft Azure. Companies do not have to update the infrastructure software themselves. Instead, the PaaS provider takes over all upgrades, patches and routine software maintenance. With PaaS solutions companies are confronted with lower risks, as they do not have to make investments in hardware and software. The development team can focus on the development of the cloud application, without having to look after the test and provisioning infrastructure.
SaaS – Software-as-a-Service
When referring to cloud services, most people think about Software-as-a-Service providers. SaaS providers provide their customers with fully functioning web-based applications. The applications are mainly aimed at business customers and can include for example web conferencing, ERP, CRM, email, time management and project tracking. Billing models for SaaS solutions can be subscription-based, usage-based or free of charge. SaaS service are quickly scalable, accessible from any place with internet access, offer user-defined service levels as well as maintenance and support bundled at the provider.
Differences between Public Cloud and Private Cloud
With a public cloud the cloud infrastructure is always located at the service provider, who also operates and maintains it. On the other hand, a private cloud is an infrastructure, which is mainly intended for companies. It is either hosted locally or in the data centre of a service provider. Private clouds offer different advantages, which are in areas such as data security and data protection, but are also often associated with increased costs. A hybrid cloud is the combination of a public and private cloud, whereby both concepts are merged to combine the advantages from both models. It can be tailored individually to each company.
The Advantages & Disadvantages of Public Clouds
A key advantage of a public cloud is the quick installation, provisioning and scalability of applications. It only takes a few minutes or hours to set up a cloud service application. It is possible to access the cloud service from any computer, smart phone, tablet or laptop with internet connection. The cloud services are easily and quickly scalable. When a company grows or if there are peak loads, then resources can be simply expanded. Ultimately, companies benefit generally from improved efficiency and lower costs. This gives them a competitive edge and can help to gain market shares. Cloud services can help start-ups to become profitable quickly without having to make investments in an internal IT infrastructure, hardware or software.
The use of public cloud services, of course, also has disadvantages. At the top of the list is the fact that security of data stored in a public cloud is cause for concern. It is often seen as an advantage that the public cloud has no geographic limitations and therefore guarantees simple access from anywhere. On the other hand, this could also mean that the server is located in another country, which has completely different security and data protection regulations. In some cases, the performance can also lead to problems if a large number of customers share the same hardware.
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