The Azure Stack HCI FAQ provides information about Azure Stack HCI connectivity with the cloud, and how Azure Stack HCI relates to Windows Server.
How does Azure Stack HCI use the cloud?
Azure Stack HCI is an on-premises hyperconverged infrastructure stack delivered as an Azure hybrid service. You install the Azure Stack HCI software on physical servers that you control on your premises.
Then you connect to Azure for cloud-based monitoring, support, billing, and optional management and security features.
This FAQ section clarifies how Azure Stack HCI uses the cloud by addressing frequently asked questions about connectivity requirements and behavior.
Does my data stored on Azure Stack HCI get sent to the cloud?
No. Customer data, including the names, metadata, configuration, and contents of your on-premises virtual machines (VMs) is never sent to the cloud unless you turn on more services, like Azure Backup or Azure Site Recovery, or unless you enroll those VMs individually into cloud management services like Azure Arc.
Because Azure Stack HCI doesn't store customer data in the cloud, business continuity disaster recovery (BCDR) for the customer's on-premises data is defined and controlled by the customer.
To set up your own site-to-site replication using a stretched cluster, see Stretched clusters overview. Stretched cluster functionality is only available in Azure Stack HCI, version 22H2.
To learn more about the diagnostic data we collect to keep Azure Stack HCI secure, up to date, and working as expected, see:
Does the control plane for Azure Stack HCI go through the cloud?
No. You can use edge-local tools, like Windows Admin Center, PowerShell, or System Center, to manage directly the host infrastructure and VMs even if your network connection to the cloud is down or severely limited.
Common everyday operations, like moving a VM between hosts, replacing a failed drive, or configuring IP addresses don’t rely on the cloud. However, cloud connectivity is required to obtain over-the-air software updates, change your Azure registration, or use features that directly rely on cloud services for backup, monitoring, and more.
Are there bandwidth or latency requirements between Azure Stack HCI and the cloud?
No. Limited-bandwidth connections like rural T1 lines or satellite/cellular connections are adequate for Azure Stack HCI to sync. The minimum required connectivity is several kilobytes per day. More services might require extra bandwidth, especially to replicate or back up whole VMs, download large software updates, or upload verbose logs for analysis and monitoring in the cloud.
Does Azure Stack HCI require continuous connectivity to the cloud?
No. Azure Stack HCI is designed to handle periods of limited or zero connectivity.
What happens if my network connection to the cloud temporarily goes down?
While your connection is down, all host infrastructure and VMs continue to run normally, and you can use edge-local tools for management. However, you wouldn't be able to use features that directly rely on cloud services. Information in the Azure portal may also become out-of-date until Azure Stack HCI is able to sync again.
How long can Azure Stack HCI run with the connection down?
At the minimum, Azure Stack HCI must sync successfully with Azure once per 30 consecutive days.
What happens if the 30-day limit is exceeded?
If Azure Stack HCI doesn’t sync with Azure in 30 consecutive days, the cluster’s connection status shows Out of policy in the Azure portal and other tools, and the cluster enters a reduced functionality mode. In this mode, the host infrastructure stays up and all current VMs continue to run normally. However, new VMs can’t be created until Azure Stack HCI is able to sync again. The internal technical reason is that the cluster’s cloud-generated license has expired and must renew by syncing with Azure.
What content does Azure Stack HCI sync with the cloud?
This depends on which features you’re using. At the minimum, Azure Stack HCI syncs basic cluster information to display in the Azure portal, including the list of clustered nodes, hardware model, and software version; billing information that summarizes accrued core-days since the last sync, and minimum required diagnostic information that helps Microsoft keep your Azure Stack HCI secure, up-to-date, and working properly.
The total size is small – a few kilobytes. If you turn on additional services, they may upload more. For example, Azure Log Analytics would upload logs and performance counters for monitoring.
How often does Azure Stack HCI sync with the cloud?
This depends on which features you’re using. At the minimum, Azure Stack HCI tries to sync every 12 hours. If a sync operation doesn’t succeed, the content is retained locally and sent with the next successful sync. In addition to this regular timer, you can manually sync any time using the Sync-AzureStackHCI PowerShell cmdlet.
If you turn on additional services, they may upload more frequently. For example, Azure Log Analytics uploads every 5 minutes for monitoring.
Where does synced information actually go?
Azure Stack HCI syncs with Azure and stores data in a secure, Microsoft-operated datacenter. To learn more about the diagnostic data we collect to keep Azure Stack HCI secure, up to date, and working as expected, see Azure Stack HCI data collection and Data residency in Azure.
Can I use Azure Stack HCI and never connect to Azure?
No. Azure Stack HCI must sync successfully with Azure once per 30 consecutive days.
Can I transfer data offline between an "air-gapped" Azure Stack HCI and Azure?
No. There's currently no mechanism to register and sync between on-premises and Azure without network connectivity.
How does Azure Stack HCI relate to Windows Server?
Windows Server is the foundation of nearly every Azure product, and all the features you value continue to release with support in Windows Server. The initial offering of Azure Stack HCI was based on Windows Server 2019 and used the traditional Windows Server licensing model.
Today, Azure Stack HCI has its own operating system and subscription-based licensing model. Azure Stack HCI is the recommended way to deploy HCI on-premises, using Microsoft-validated hardware from our partners.
Which guest operating systems are supported on Azure Stack HCI?
Azure Stack HCI supports several guest operating systems. For more information, see Supported Windows guest operating systems for Hyper-V on Windows Server.
Can I upgrade from Windows Server to Azure Stack HCI?
At this time, there's no in-place upgrade from Windows Server to Azure Stack HCI. However, you can migrate your VM workloads from Windows Server to Azure Stack HCI using Azure Migrate. For more information, see Overview of Azure Migrate based migration for Azure Stack HCI (preview).
What Azure services can I connect to Azure Stack HCI?
For an updated list of Azure services that you can connect Azure Stack HCI to, see Managing hybrid capabilities on Azure Stack HCI with Azure services.
How do I identify an Azure Stack HCI server?
In Azure portal, go to your server. If the server is Arc registered, you should be able to see the OS version and overall Azure Stack HCI version.
Use the following PowerShell command to query for the OS name and OS version.
Get-ComputerInfo -Property 'osName', 'osDisplayVersion'
Here’s some example output:
OsName OSDisplayVersion
------ ----------------
Microsoft Azure Stack HCI 23H2