Posts Tagged Comparison

Technical comparisons of AWS and Azure

Update: This post was written in 2011 when Windows Azure was PaaS only. The Spring 2012 IaaS features now allow more direct comparisons, but the PaaS principles discussed in this post are still relevant.

AWS is the market leader of cloud computing, by virtue of its early entry, rapid innovation and monopolisation of the definition of cloud computing. Microsoft is a viable contender with their established customers, channels and developers as well as a sound offering backed by a company that is “All in”.

Little surprise then that customers, particularly those with a Microsoft bias, that are looking at public cloud platforms want to compare the de-facto standard of AWS with the apparently familiar world of Windows Azure. Business then turns to technical people for an opinion and a simple explanation of the differences between them.

On the surface, a technical person can draw parallels. Windows Azure (AppFabric) Queues map to Amazon Simple Queue Service. SQL Azure maps to Amazon Relational Database Service and, more recently, Windows Azure AppFabric Caching maps to Amazon ElastiCache, and so on. But those are services offered on the platform, so while you can compare and map individual services, it becomes difficult to provide a technical comparison of the overall platforms.

The fundamental building block of AWS applications is the EC2 instance and on Windows Azure it is the compute role (mostly web and worker roles). EC2 is a fully fledged virtual machine and Azure roles are containers for compute resources. (Drawing parallels between EC2 and Windows Azure VM Roles does a disservice to EC2, as Azure VM roles are not the building block of Azure applications.)

The importance of EC2 as a basic building block breaks down most of the technical comparisons between the two platforms. One may, for example map Windows Azure Table Storage, as a NoSQL database, to Amazon SimpleDB. But, with EC2 as a building block, SimpleDB is not the popular NoSQL choice on AWS, where MongoDB and Redis run well. Also, EC2 allows anything to be run (although some may not be recommended), giving EC2 an unfair edge over Windows Azure. You can, for example, run SOLR on Linux for search on EC2 and it manifests itself as a first class service, whereas no search service exists on the Windows Azure platform.

In turn, Windows Azure roles, as the container for applications and the basic building block, have advantages over EC2. Windows Azure roles require significantly less hand holding, configuration and management than EC2. There is no Chef for Windows Azure. The Windows Azure AppFabric takes care of keeping the roles running smoothly. (AWS is catching up with CloudFormation and the Java oriented Elastic Beanstalk, but it still cannot be compared to the Windows Azure fabric controller).

It would be easy to say that Windows Azure is PaaS and Amazon Web Services is IaaS, so that is where the comparison should be made. But, firstly AWS is not IaaS, and secondly all cloud vendors are moving further up the stack, providing more services that can be consumed instead of the infrastructure services. Amazon’s ElastiCache is a good example of this, where a component that previously had to be hosted in EC2 instances is now made available as a service. AWS will continue, I am sure, to add more services and the infrastructure appearance of their model will be unimportant in a few years’ time. At the same time, Microsoft has the opportunity and engineering resources to add really good services and even entire application suites to their platform — further confusing the comparisons.

So when business asks for a comparison between the two, work with them to do a higher level comparison that makes sense in their particular environment. Don’t cheat by trying to map low level services, features and prices — they look eerily similar at that level and you won’t find the droids you are looking for. Rather try something like this,

  • Map out a general architectural picture for each of the platforms
  • Decide which components are less architecturally significant, so that compromises can be made (and there are always compromises)
  • Factor in the business and internal IT attitude towards Microsoft, anti-Microsoft and Amazon
  • Look at existing IT support processes and how they would fit in with each platform.
  • Work out, more or less, what the development, hosting and support costs will be for each platform. Comparing EC2 pricing to Azure Role pricing is not enough.
  • Look at the application roadmap to determine if it looks like it will add high degrees of specialisation, forcing it down the AWS route, or integration with existing services and applications, tending it more towards Windows Azure.
  • Get internal IT on board, they probably won’t like either of them, so you need to get working on them early.

Simon Munro



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