For those companies that can’t yet move to the cloud, have certain workloads that can’t move to the cloud, or have limited to no internet access, Microsoft has options to build your own private on-prem cloud via Azure Stack and Azure Arc. I’ll focus this blog on using these products to host your databases.

Azure Stack is an extension of Azure that provides a way to run apps and databases in an on-premises environment and deliver Azure services via three options:

Azure Stack Hub: Run your own private, autonomous cloud—connected or disconnected with cloud-native apps using consistent Azure services on-premises. Azure Stack Hub integrated systems are comprised in racks of 4-16 servers built by trusted hardware partners and delivered straight to your datacenter. Azure Stack Hub is built on industry standard hardware and is managed using the same tools you already use for managing Azure subscriptions. As a result, you can apply consistent DevOps processes whether you’re connected to Azure or not. The Azure Stack Hub architecture lets you provide Azure services for remote locations with intermittent connectivity or disconnected from the internet. You can also create hybrid solutions that process data locally in Azure Stack Hub and then aggregate it in Azure for additional processing and analytics. Finally, because Azure Stack Hub is installed on-premises, you can meet specific regulatory or policy requirements with the flexibility of deploying cloud apps on-premises without changing any code. See Azure Stack Hub overview

Azure Stack Edge: Get rapid insights with an Azure-managed appliance using compute and hardware-accelerated machine learning at edge locations for your Internet of Things (IoT) and AI workloads. Think of it as a much smaller version of Azure Stack Hub that uses purpose-built hardware-as-a-service such as Pro GPU, Pro FPGA, Pro R, and Mini R. The Mini is designed to work in the harshest environment conditions, supporting scenarios such as tactical edge, humanitarian and emergency response efforts. See Azure Stack Edge documentation

Azure Stack HCI (preview): A hyperconverged infrastructure (HCI) cluster solution that hosts virtualized Windows and Linux workloads and their storage in a hybrid on-premises environment. Think of it as a virtualization fabric for VM or kubernetes hosting – software only to put on your certified hardware. See Azure Stack HCI solution overview

These Azure Stack options are almost all VMs/IaaS, with no PaaS options for data services such as SQL Database (the only data service available is SQL Server in a VM). It is integrated certified hardware and software run by Microsoft, just plug in and go. For support, there is “one throat to choke” as the saying goes. It is a great option if you are disconnected from Azure. It extends Azure management and security to any infrastructure and provides flexibility in deployment of applications, making management more consistent (a single view for on-prem, clouds, and edge). It brings the Azure fabric to your own data center but allows you to use your own security requirements. Microsoft orchestrates the upgrades of hardware, firmware, and software, but you control when those updates happen.

Azure Arc is a software only solution that can be deployed on any hardware, including Azure Stack, AWS, or your own hardware. With Azure Arc and Azure Arc-enabled data services (preview) you can deploy Azure SQL Managed Instance (SQL MI) and Azure Database for PostgreSQL Hyperscale to any of these environments, which requires kubernetes. It can also manage SQL Server in a VM by just installing an agent on the SQL server (see Preview of Azure Arc enabled SQL Server is now available). Any of these databases can then be easily moved from your hardware to Azure down the road. It allows you to extend Azure management across your environments, adopt cloud practices on-premises, and implement Azure security anywhere you choose.

This allows for many options to use Azure Arc on Azure Stack or on other platforms (click to expand):

Some features about Azure Arc:

• It can be used to solve for data residency requirements (data sovereignty)
• It is supported in disconnected and intermittently connected scenarios such as air gapped private data centers, cruise ships that are off the grid for multiple weeks, factory floors that have occasional disconnects due to power outages, etc.
• Customers can use Azure Data Studio (instead of the Azure Portal) to manage their data estate when operating in a disconnected/intermittent connected mode
• Could eventually support other products like Azure Synapse Analytics
• Can use larger hardware solutions and more hardware tiers then what is available in Azure, but have to do your own HA/DR
• You are not charged if you shut down SQL MI, unlike in Azure, as it’s your hardware, where in Azure the hardware is dedicated to you even if you are not using it
• With Arc you are managing the hardware, but with Stack Microsoft is managing the hardware
• Can use modern cloud billing models on-premises for better cost efficiency
• With Azure Arc enabled SQL Server, you can use the Azure Portal to register and track the inventory of your SQL Server instances across on-premises, edge sites, and multi-cloud in a single view. You can also take advantage of Azure security services, such as Azure Security Center and Azure Sentinel, as well as use the SQL Assessment service
• Azure Stack hub provides consistent hardware, but if you use your own hardware you have more flexibility and possibly cheaper hardware costs

These slides covers the major benefits of Azure Arc and what the architecture looks like:

Looking at the differences when you are connected directly vs connected indirectly (i.e. an Arc server is not connected to the Internet so must coordinate with a server that is connected):

Here is what an Azure Arc data services architecture looks like:

Some of the top use cases we see with customers using Azure Stack and/or Azure Arc:

• Cloud-to-cloud failover
• On-prem databases with failover to cloud
• Easier migration: Deploy locally, then flip a switch to go to cloud

This slide provides details on the differences with SQL databases (click to expand):

More info:

Understanding Azure Arc Enabled SQL Server

What is Azure Arc Enabled SQL Managed Instance

Build hybrid and multicloud architectures with Azure hybrid solution architectures