There has been some confusion around what Azure Stack is right after the announcement at Microsoft Ignite in Chicago. I will try to do a short and high-level clarification based on that what I got from the sessions and I like to invite the Product Group to reach out to me if I got something wrong.
First of all Azure Stack is not a Windows Azure Pack 2.0! Even if both products sounds very similar to each other. But let me explain that to you with the help of the IaaS VM scenario.
Windows Azure Pack is just a HTML 5 portal that provides you with an Azure like self-service portal for your on-premises datacenter. It depends on System Center 2012 R2 VMM and SPF (IaaS VM scenario) and has a different VM model concept than Azure. Furthermore it consists only of one resource provider for the IaaS VM scenario the so called VM clouds resource provider and it has several other resource providers for other services.
Azure Stack is a complete new technology bringing Azure into your datacenter and finally makes the Cloud OS story a real consistent story! Based on the Azure Resource Manager Azure Stack and Microsoft Azure are sharing the same VM model concept. It is completely identical. That means you are creating VM templates only once and it does not matter if you are using them with Azure or Azure Stack! Azure Stack consists of three resource providers for the IaaS VM scenario compute, network and storage.
Let us have a look at the storage resource provider as an another example for the difference between Azure Stack and Windows Azure Pack. Azure Stack will offer you two different storage types locally redundant storage (LRS) and geographically redundant storage (GRS). Windows Azure Pack cannot offer you a storage type because it does not have any storage resource provider. For different storage types Windows Azure Pack depends on VMM and the tenant has no possibility to choose between different storage types.
I hope you got a clue that Azure Stack and Windows Azure Pack are totally different! If not here is a quote from my previous blog post about the Ignite announcements.
So Azure Stack is the replacement for Windows Azure Pack and will provide you with a consistent Microsoft Azure cloud experience for your on-premises datacenter. Yes, you got it right Microsoft will provide you with Azure technology for your on-premises datacenter and it is called Azure Stack. Same API, same experience and same technology.
I highly recommend to watch the Ignite sessions about Azure Stack to get a better understanding what Azure Stack is.