Microsoft's original three server partners for its Azure Stack hybrid computing appliance are officially taking orders as of today, July 10.

Microsoft hasn't yet made the final Azure Stack code available to Dell EMC, HPE, and Lenovo, but the three are expecting to start shipping their first Azure Stack servers to customers within the next couple of months.

Update: A Microsoft spokesperson said today, July 10, that its partners are now "in validation mode based on the code shipped in the Azure Stack Development Kits (ASDK)." The Azure Stack servers should begin shipping to customers starting in September 2017.

Microsoft officials recently made public a downloadable Azure Stack pricing and licensing datasheet, signaling the product's imminent availability.

Microsoft is describing Azure Stack as "an extension of Azure." After the initial purchase of Azure Stack, customers will only pay for Azure services that they use from general availability, forward ("pay-as-you-use" pricing). The current one-node offering meant for dev/test will continue to be free after general availability.

Azure Stack comes in the form an appliance built to run on specific server hardware. It provides customers with many of the pieces of Microsoft's Azure public-cloud platform in a form they can run inside their own or partners' on-premises datacenters.

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Microsoft is touting Azure Stack as a truly consistent hybrid-cloud platform. It will allow users to use Azure public cloud services against data stored in Azure Stack on premises, and deploy the same Azure-services-based applications on both the public Azure cloud and Azure Stack.

Microsoft and its partners are positioning Azure Stack as well suited for users with applications and workloads that have strict compliance requirements, as well as for developers who want to create applications on premises that can run on both Azure and Azure Stack.

Azure Stack will be available only via Enterprise Agreements and from Cloud Service Providers. Azure Stack services like virtual machines, Azure Storage, App Service, and Azure Functions will be metered and charged on a consumption basis. Customers will be able to use on-premises Windows Server and SQL Server licenses with Azure Stack. But as Dell EMC Principal Consultant Augusto Alvarez recently blogged, the Azure Stack versions of these services are cheaper than the Azure ones.

The HPE ProLiant for Microsoft Azure Stack version starts at $300,000 to $400,000 for the hardware and support, depending on the configuration. Dell hasn't provided pricing for its hardware and support for its Dell EMC Cloud for Microsoft Azure Stack, nor has Lenovo for its Lenovo ThinkAgile SX for Microsoft Azure Stack.

Update: The pricing for Lenovo ThinkAgile SX for Microsoft Azure Stack is $236,000 for a four-node configuration.

Dell, HPE, and Lenovo aren't the only hardware partners who have committed to Azure Stack. Cisco, Huawei, and Avanade are all working on providing Azure Stack appliances, too.

Microsoft's original plan was to deliver Azure Stack before the end of 2016 and allow customers to run it on the hardware of their choice. Last year, Microsoft shifted gears, requiring users to purchase Azure Stack as an appliance on a small set of pre-selected servers, and pushed back the product's release until mid-2017.