In-Depth

.NET Survival Guide: Cloud and Software as a Service

• By Mark Michaelis
• 01/01/2011

Cloud and Software as a Service
Cloud computing solutions vary considerably, yet claim superior privacy, security and scalability over on-premises deployments that also require the expense of an IT department to manage them. Different cloud approaches differ in implementation, however, with various models allowing for the renting of rack space, dedicated servers, virtual machine (VM) time and even application CPU time.

This diversity of cloud computing solutions can be broken down into three primary categories, each building on top of the other:

• Infrastructure as a Service (IaaS): IaaS provides the hardware (rack space, servers, network connectivity, electrical power and so on) along with the base OS installation and (optionally) database platforms. Customers with this level of service generally have remote access to the environment, along with the responsibility for all software-related installation, updates and configuration. Support for scalability is through the explicit requisitioning of additional hardware and then configuration to manage and enable the scalability.
  Examples: Amazon Web Services and Windows Azure Virtual Machine Role
• Platform as a Service (PaaS): PaaS enables the deployment of applications into a hosting environment on which the applications run. It includes automated service management with application-lifetime management, load balancing, platform patches and more, leaving only configuration of the app to the customer. PaaS allows the application to automatically scale to demand, so that even the concept of how many servers are executing the application is abstracted away.
  Examples: Microsoft Azure AppFabric and ASP.NET Hosting
• Software as a Service (SaaS): This is where an application itself is hosted and customers subscribe to the functionality of the application. Although the application may be deployed across a myriad of devices and locations, the customer just sees it as a software application that's available when needed.
  Examples: Gmail, bing.com and Microsoft Office 365

PaaS provides the ideal solution for developers working to enable SaaS deployments for their organizations. PaaS enables focus on an app's business value, rather than the necessary but auxiliary infrastructure that hosts the app. PaaS also provides companies with the lowest level of commitment needed to provide SaaS to their customers.

There are some drawbacks to consider with PaaS, though these are growing less severe over time. First, there remains a significant level of complexity when it comes to managing connections to other applications that are still running on-premises. Providing secure access to intranet-based LOB systems is still non-trivial. Similarly, if data storage sizes are large, the costs of storage in the cloud can appear expensive.

PaaS platforms such as ASP.NET Hosting generally provide smooth migration of identical code from your own premises into the cloud. Windows Azure AppFabric does require some application tweaks to make the jump, but as the technology improves, this pain point will almost certainly diminish. In both cases, there's an on-premises means for development testing prior to deployment, which is important because deploying to solutions such as Windows Azure is generally an order of magnitude slower than deploying to an on-premises server. This factor, coupled with the possibility that running in the cloud could expose discrepancies with the on-premises behavior, makes automated deployment (using Windows Azure SDK-provided Windows PowerShell cmdlets) an important time-saver in the ALM process.

There's little doubt that for startup organizations, the cloud is an intriguing target for application development. However, cloud computing may not make sense for organizations that have considerable investment in their own datacenters. In either case, managers must factor in the on-premises costs of disaster recovery, IT support staff, security, scalability and highly available connectivity when making a decision.

In Summary Microsoft AppFabric and ASP.NET Hosting promise a seamless path for ASP.NET applications to reside both on-premises and in the cloud.