Which is Right for You: IaaS, PaaS or SaaS?

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There are various ways a cloud-based service is consumed and utilized. In the world of cloud computing, there are three primary approaches to cloud-based services:

  • Infrastructure as a Service (IaaS)
  • Platform as a Service (PaaS)
  • Software as a Service (SaaS)

Microsoft offers cloud services based on its widely used on-premises software products.

  • Office 365 is SaaS, which provides an online version of MS Office Suite (Office Web Apps) along with SharePoint Server, Exchange Server and Lync Server.
  • Windows Azure is both IaaS and PaaS, which makes the Windows Server operating system and other features available as services.


Infrastructure as a Service (IaaS)

With the IaaS model, you can outsource the elements of infrastructure like Virtualization, Storage, Networking and Load Balancers, to a cloud provider like Microsoft.

To deploy your applications to the Cloud, you install OS images and related application software on the cloud infrastructure. In this model, it’s your responsibility to patch/update/maintain the OS and any application software you install. The cloud provider typically will bill you on computing power by the hour and the amount of resources allocated and consumed (as per its service level agreement or SLA).

For example, using Windows Azure, you can set up new Windows Server and Linux virtual machines and adjust your usage as your requirements change. You only have to pay for the service that you use.


Infrastructure services_small


One of the biggest benefits of IaaS is that it provides granular control, in which you choose the core components for your infrastructure. By pooling your computing and storage resources you can scale with ease and speed to meet the infrastructure needs of your entire organization or individual departments, globally or locally.

Platform as a Service (PaaS)

With the PaaS model, you get a core hosting operating system and optional building block services that allow you to run your own applications or third-party applications. You need not be concerned about lower level elements of Infrastructure, Network Topology, Security and Load Balancers — all this is done for you by the Cloud Service Provider. The Provider gives you a fully functional OS with major platform software.

Microsoft Windows Azure as PaaS can be used as a development, service hosting and service management environment. SQL Azure can provide data services, including a relational database, reporting and data synchronization. Both Windows Azure and SQL Azure are the key components of the Azure Cloud Platform. With this platform, you can focus on deploying your custom applications and can easily configure your applications to scale up or down as demands change.

Microsoft Azure platform as PaaS can support different roles, such as Worker and Web. For example, you can run web applications with the Web Role, as well as host middle tier applications, such as Workflow, in the Worker Role. Similarly, SQL Azure provides Microsoft’s core relational database engine as a platform service.

One of the key benefits of PaaS is that you need not be concerned about running OS or updates (service packs) and hardware upgrades. The Provider regularly patches your OS, updates platform features (such as the core .NET platform or SQL database engine) and updates hardware on demand to meet your demand.

The figure below (taken from the official Windows Azure website) demonstrates how the Cloud Services technology from Azure can be used PaaS.

Windows Azure
Microsoft Office 365 is SaaS that provides these types of services, which include SharePoint Online, Exchange Online, Lync Online and Office Professional Plus. Most of these online services have a subset of the features available on their on-premises counterparts. Microsoft Online Services are subscription-based, on-demand applications and hosted services, providing your organization with a consistent experience across multiple devices.

Office 365Below are some key services offered by Office 365 as SaaS:

Office Web Apps: Create and edit Word, Excel, PowerPoint and OneNote files via a web browser.

Office Mobile Apps: Access, edit and view Word, Excel and PowerPoint documents on iPhones and Windows Phones. Use the OneNote, Lync Mobile and SharePoint Newsfeed apps on most devices.

Hosted email: Business-class email, shared calendars, 25 GB of storage space per user and the ability to use your own domain name.

Active Directory integration: Manage user credentials and permissions. Single sign-on and synchronization with Active Directory.

Simple file sharing: SkyDrive Pro gives each user 7 GB of personal storage they can access from anywhere that syncs with their PC. Easily share files internally and externally and control who sees and edits them.

Web conferencing: Conduct meetings over the web with HD video conferencing, screen sharing and instant messaging.

Public website: Market your business with a website that is easy to set up, using your own company domain name.

Intranet Team Sites: SharePoint sites provide workspaces with customizable security settings for individual teams within the organization.

Site Mailboxes: Store and share email and documents in project-specific folders, allowing for easier team collaboration.

e-Discovery Center: Tools to support compliance. Search across SharePoint sites and Exchange mailboxes.

Advanced Voice: Hosted voice mail support with auto attendant capabilities.

Business Intelligence: Create and manage interactive dashboards with multiple data sources.

Which is Right for You: IaaS, PaaS or SaaS?

Before you consider IaaS, PaaS or SaaS, you should think about the trade-off between “Effort to Manage” and “Level of Control” to make the best decision for your needs. In general, the IaaS model provides the highest level of control among the three (yet may be more costly). The SaaS model takes the least effort to manage (and may be comparatively less costly).

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