Initial cloud hosting offerings focused on the LAMP stack, however in the past 6 months several viable Windows cloud hosting options have become available. Both Rackspace and Amazon now have Windows cloud offerings and most notably Microsoft has just launched Windows Azure which is actually a new cloud operating system and not fully compatible with existing Windows applications.
Provided your web site/application is running on the Windows stack now (Windows Server/IIS/ASP.NET) it should be compatible with the cloud offerings from Rackspace Cloud, Amazon, GoGrid and others. In this article I will focus on the big two cloud providers (Rackspace and AWS) as well as the new Windows Azure service which could be consider as worthy rivals to traditional Windows Hosting.
Rackspace Cloud provides two Windows cloud hosting offerings, Cloud Sites and Cloud Servers. Cloud Sites is a standardised product which provisions a website with a fixed windows setup – Windows Server 2008/IIS 7 and ASP.NET (2.0 and 3.5 both supported). If you run a website powered by a Windows based content management system (CMS), or customer relationship management system the Rackspace Cloud Sites will probably be the best option. Cloud Sites only provides FTP access to the server and no Remote Desktop access to the server is possible. Cloud Sites basic package starts at $150 per month plus $10 per month for a 100MB SQL Server database.
If the application setup is more complicated and operating system access is required, Rackspace Windows Servers will be the best option which starts at about $112 per month for 2 GB RAM / 80 GB Hard Drive server (smaller instances are also available). This service is currently in beta and a major weakness is that this does not come with a SQL Server installation and users are required to make their own arrangements.
Amazon AWS has been offering Windows cloud hosting options since early 2009. 1.7 GB of memory / 160 GB (1 core) EC2 instance are priced at $80 per month. SQL Server is available, however it does get expensive as a lease on SQL Server standard edition starts at $750 per month.
The new entrant to Windows cloud hosting is Microsoft with its new Windows Azure service. As noted above, all Windows applications will need at least some modification to run on Azure. The biggest change is probably with SQL Server, where the cloud variant (SQL Azure) has numerous incompatibilities making migration a challenge at best. SQL Azure databases are priced at $10 per month for 1GB and $100 per month for 10GB.
Windows Azure pricing is slightly different from Rackspace and AWS which bundle a the RAM/CPU/Drive space in a virtual server package. Windows Azure is broken out between compute ($84 per month), storage ($0.15 per GB per month), storage transactions ($0.01 for 10,000 transactions) and data transfer at $0.10 in / $0.15 out per GB. This makes comparisons difficult in pricing, however Azure looks to be slightly more expensive than AWS and cheaper than Rackspace (the $10 per month SQL Azure instances can make Azure a lot cheaper as n0 equivalent exists on the other providers).
For an overview of Windows Azure see Windows Azure First Impressions , or Who Will Use Azure
Summary
Which of the providers is best really depends on your needs. If it is a simple website then Rackspace Cloud Sites is definitely the way to go. If you have a more complex application (which for example runs windows services or requires access to the OS) then AWS is probably the best bet. Azure promises to be the ultimate windows cloud with features such as SQL Azure databases which can be scaled up on demand, although it does have compatibility issues with existing windows apps and is still in its infancy (having just been released in February 2010).
(note – I have used monthly charges to compare pricing although all the above providers bill the services hourly)