Using Azure Stack HCI on a single server

Applies to: Azure Stack HCI, version 21H2

This article provides an overview of running Azure Stack HCI on a single server, also known as a single-node cluster. Using a single server minimizes hardware and software costs in locations that can tolerate lower resiliency. A single server can also allow for a smaller initial deployment that you can add servers to later (scaling out).

Along with the benefits mentioned, there are some initial limitations to recognize.

  • You must use PowerShell to create the single-node cluster and enable Storage Spaces Direct.
  • Single servers must use only a single drive type: Non-volatile Memory Express (NVMe) or Solid-State (SSD) drives.
  • Stretched (dual-site) clusters aren't supported with individual servers (stretched clusters require a minimum of two servers in each site).
  • To install updates using Windows Admin Center, use the single-server Server Manager > Updates tool. Or use PowerShell or the Server Configuration tool (SConfig). For solution updates (such as driver and firmware updates), see your solution vendor. You can't use the Cluster Manager > Updates tool to update single-node clusters at this time.
  • Operating system or other updates that require a restart cause downtime to running virtual machines (VMs) because there isn't another running cluster node to move the VMs to. We recommend manually shutting down the VMs before restarting to ensure that the VMs have enough time to shut down prior to the restart.

Prerequisites

For hardware, software, and network requirements see What you need for Azure Stack HCI.

Comparing single-node and multi-node clusters

The following table compares attributes of a single-node cluster to multi-node clusters.

Attributes Single-node Multi-node
Full software-defined data center (SDDC) stack (hypervisor, storage, networking) Yes Yes
Storage Spaces Direct support Yes Yes
Software Defined Networking (SDN) support Yes Yes
Native Azure Arc integration Yes Yes
Managed through Windows Admin Center and Azure portal Yes Yes
Azure billing/registration Yes Yes
Charged per physical core Yes Yes
Support through Azure Yes Yes
Connectivity (intermittent or connected) Yes Yes
Azure benefits on Azure Stack HCI Yes Yes
Activate Windows Server Subscriptions Yes Yes
Azure Defender and Secured-core Yes Yes
Azure Kubernetes Service on Azure Stack HCI (AKS-HCI) Yes 1 Yes
Azure Virtual Desktop Yes Yes
Azure Site Recovery Yes Yes
Azure Stack HCI: Stretch cluster support No Yes
Use Graphics Processing Units (GPUs) with clustered VMs Yes Yes

1 Limited support, AKS on Azure Stack HCI is in preview on single-node clusters.

Known issues

The following table describes currently known issues for single-node clusters. This list is subject to change as other items are identified: check back for updates.

Issue Notes
SBL cache is not supported in single-node clusters. All-flash, flat configuration with Non-volatile Memory Express (NVMe) or Solid-State Drives (SSD) must be used.
Windows Admin Center doesn't support creating single-node clusters. Deploy single server with PowerShell.
Windows Admin Center cosmetic user interface (UI) changes needed. Doesn't limit Live Migration within the same cluster; allows affinity rules to be created, etc. Actions will fail without any harm.
Windows Admin Center pause server fails since it tries to drain the server. Utilize PowerShell to pause (suspend the server).
Windows Admin Center and PowerShell fail to create a volume. Use PowerShell to create the volume without "StorageTier" parameter. For example, New-Volume -FriendlyName "Volume1" -Size 1 TB -ProvisioningType Thin.
Cluster Aware Updating (CAU) doesn't support single-node clusters. Update using PowerShell, the Server Configuration tool (SConfig), or Windows Admin Center (through server manager). Learn more
Adding a node to scale out the single-node cluster doesn't automatically change the Storage Spaces Direct FaultDomainAwarenessDefault. FaultDomainAwarenessDefault can be changed manually from PhysicalDisk to StorageScaleUnit.

Next steps