Azure Stack HCI: Hyper-converged, but not as Azure as you’d think

Microsoft has launched Azure Stack HCI, which provides hyper-converged infrastructure (HCI) in which virtualised environments can run on local hardware with simplified access to the Azure cloud for hybrid cloud operations.

The branding makes it look like an addition to the existing Azure Stack environment, which allows local datacentres to run Azure software on-site and to benefit from Azure cloud services, but it is a rebranding and compatibility has its limitations.

Azure Stack HCI provides hyper-converged infrastructure functionality with a two-node minimum configuration and virtualisation via the Hyper-V hypervisor, which runs virtual machines with virtualised storage from Storage Spaces Direct, aka S2D, a software-defined storage feature that originated in Windows Server 2016.

Azure Stack HCI was previously called Windows Server Software Defined (WSSD), so the move to becoming Azure Stack HCI is a rebranding move.

What may lie behind it is that WSSD is not sufficiently widely deployed to figure in IDC’s numbers for hyper-converged infrastructure.

According to the most recent figures, from October 2018, HCI from Nutanix and VMware (ESX, vSAN, NSX, vCenter) each take around 34% of the market, while those from Dell EMC (VxRails), Cisco and HPE each form around 5%.

WSSD has been buried in the “others” category, which accounts for about 16% of the market. Microsoft Azure, meanwhile, is firmly placed as number two in the public cloud market with – according to Microsoft – revenue growth of around 90% every year.

WSSD connected to the Azure public cloud in pretty much the same way as other Windows network solutions, via a virtual private network (VPN), or better still with Microsoft’s ExpressRoute, which provides dedicated Azure connectivity via an MPLS-enabled VPN connection.

With Azure Stack HCI, customers can migrate virtual machines from on-premise to cloud, or to set the Microsoft cloud as a target for local backup. Azure does also offer this functionality to other hyper-convergence platforms, however.

Azure Stack HCI is manageable via the Azure authentication service, like any other Windows Server.

Azure Stack HCI doesn’t seem to have a great deal of kinship to other Azure products, however. If an application has been written to interface with Azure services, it won’t function on Azure Stack HCI, although it will with Azure Stack. 

Another difference between Azure Stack on-site or Azure in the cloud and Azure Stack HCI is the medium of consumption.

The first two are billed according to quantity of service resources used per month. Azure Stack HCI is bought discretely with additional options such as the SDN Azure Network Adapter or Azure Security Center monitoring modules.  

We should note, in this regard, that Azure Stack is generally supplied pre-installed on approved servers, while Azure Stack HCI is deployable by the customer on a wide range of server hardware.

Paul Rosen