Cloud Service Models: IaaS, PaaS, SaaS

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What is Cloud service models?

Cloud service models refer to different ways in which cloud computing services are delivered to users over the internet. There are three main cloud service models: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).

Types of Cloud Service Models

Infrastructure-As-A-Service (IaaS)

The IaaS model is based on providing data center facilities to clients over the Internet. This model is offered by firms such as Amazon Web Services, Google Compute Engine, Microsoft Azure, and others. The data centers are virtual facilities that allow clients to rent hardware, such as one or many CPUs, memory and storage space, networking facilities, software to manage the facility, some basic security software, such as a firewall, and utilities. The facilities are identical to what would be created by the actual purchase of hardware on-premises, except that these are made available over the Internet.

Vendors who provide IaaS products ensure the maintenance of hardware and software, provide service level guarantees (based on what clients need) and update the hardware and features as and when they are available.

The client or user can then install their application software on the infrastructure they have rented. This includes system software, such as operating systems and networking software, and also applications that they need, such as databases, servers, enterprise software, and so on. The idea is similar to renting an empty apartment, with basic facilities such as plumbing and utilities, like water and electricity. The furnishing and fixtures are provisioned by the renter, based on the latter’s needs.

In this model, the responsibility of the provider is restricted to ensuring that the system is up and running as promised in the contract, and does not extend to the applications and their functioning. IaaS pricing is based on usage – rentals may be by time units, such as minutes, hours, or months; and rentals may be priced on facilities provided, such as the number of CPUs, and the extent of memory and storage.

IaaS facilities are often acquired by start-up firms that want to build or deploy a cloud-based product. They may not have the capital required to acquire all the needed hardware and facilities for their product and find it easier to rent facilities at a fraction of the cost.

Using the cloud also reduces the time required to have access to an infrastructure, considerably reducing the time to deploy their product in the market. This model is also used by firms that have established systems and want to try out something new, without having to buy and deploy new hardware. They can test out and experiment on the cloud, without touching their existing setup.

Platform-As-A-Service (PaaS)

The PaaS facility provides users with several tools and packages with which an IT solution can be built and deployed on the cloud. The PaaS model builds on and extends the IaaS model, where special software is included over and above the infrastructure.

For example, a typical PaaS provided by vendors, such as Microsoft or Amazon, will have an infrastructure, with computing devices and memory and storage, and will also give additional facilities such as an operating system, program development libraries, and possibly included databases, and other packages. The customer can use these tools to rapidly develop applications. The analogy for PaaS is that of renting a furnished apartment where most of the facilities for a living are already available and the renter can start living there with only her personal effects.

PaaS is also widely used by start-ups and innovators who want to build an application quickly and deploy it on the full scale. Most PaaS providers have facilities for ‘plugins’ or commercial products that clients can have access to, at a nominal cost.

For example, clients who are building an enterprise application, on a PaaS cloud, can access an email or messaging ‘plugin’ application that helps them build mail or messaging features into their product, without building these applications on their own.

Software-As-A-Service (SaaS)

SaaS is one of the oldest and best-known ways of offering services over the cloud. Almost all Internet users are familiar with applications such as email that are often provided for free by firms like Google and Yahoo! These applications are available to anybody with an Internet connection and a browser. Further, these applications provide their full functionality regardless of the type of hardware or operating system from where they are accessed. The IDOS company offers its product as a SaaS product.

Zoho Office is another example of a SaaS product that has rich functionality and competes almost directly with desktop applications. Zoho’s offering is a suite of office productivity applications, such as a word processor, a spreadsheet, a presentation tool, and others that are available on the cloud. A firm can rent the entire Zoho Office for its employees, and each employee user can then use the office tools on the Internet, without having to download and install anything on their own computing devices. They can save their work on the cloud and also share their work with their colleagues easily.

Zoho backs up all user files, upgrades their software, and enables access to users from anywhere. Zoho prices their office suite based on usage and clients need to pay for only what they need. Zoho’s direct competitor is Microsoft Office which earlier had to be installed, was priced on a per-user license basis, and was available only on the device on which it was installed.

The SaaS model can be best compared to renting a fully serviced apartment where renters have to do little to run or maintain their surroundings, and focus instead on living and enjoying their apartment. The SaaS model builds on the IaaS and PaaS models, with the difference that the focus is on the application or functionality that is provided. SaaS application users have access to the application alone, and cannot change or manage the underlying hardware or systems software. Unless explicitly provided, users cannot also change any aspect of the application other than their settings.

Many enterprise application sellers provide their products through the SaaS model. is a prominent customer relationship management product that is available through its SaaS platform. Client firms rent accounts, for a given number of users, and their customers, and run the application as if they had purchased and hosted it on their premises. assists its clients with customization and management of the product, if required, and provides upgrades when they are available, otherwise, clients run the software application on their own.

Innovators and start-ups rely on the SaaS model, as is evident in the case of IDOS. This model allows products to be made available to customers in a convenient manner, over any device, and in any location where the Internet is available. The model also enables potential customers to sample the product, possibly collaborate with others, and experience the features without the bother of downloading and installing anything.

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