The cost associated with Outbound Data Transfer is very important when you consider bridging your On-premise network with Windows Azure.

Yes, when I said cost I indeed meant the $ amount which is involved. The good news however is that all the Inbound Data sent to Azure is free. The outbound data is all what really matters.

As per Microsoft

Outbound data is charged based on the total amount of data moving out of the Windows Azure datacenters via the Internet in a given billing cycle. Data transfers between Windows Azure services located within the same datacenter are not subject to any charge. The first 5 GB of outbound data transfers per billing month are also free.

Lets talk about this simple scenario – You have deployed SQLServer on a Windows Azure Virtual Machine. Data out of the SQLServer database will be accessed by clients which are located in your On-premise data center. Below diagram will explain the scenario.

Note – This is a high level diagram and doesn’t explain the actual network intricacies which are involved while bridging your network with Azure.

All the outbound data which is flowing out of the Azure data center is a cost ($) factor for you and inbound data sent is free.

How much should I pay?  Well,that really depends on your usage.

First 5 GB a month is free and beyond that cost is like(As of today) -

Ref – http://www.windowsazure.com/en-us/pricing/details/data-transfers/

Note – Always ref http://www.windowsazure.com for any pricing estimates as these numbers($) tend to change.

Conclusion

Analyzing and understanding various cost factors which are involved with Windows Azure is one of the key areas an Architect should focus on and comparing this costs with ongoing on premise operational costs will help management get a clear picture.

Thanks for reading and keep watching this space for more !