In an HCI cluster, adding server nodes increases the storage capacity, improves the overall storage performance of the cluster, and provides more compute resources to add VMs. Before adding new server nodes to an HCI cluster, complete the following requirements:

• Verify that the processor model HBA and NICs are of the same configuration as the current nodes on the cluster and PCIe slots.
• Ensure that all disk types and the amount in each node are the same as the node in use. Do not combine two different disk types in the same cluster or node. For example, you cannot combine SATA and SAS HDD/SSD drives in the same node or cluster. The following table lists the supported options for expanding storage capacity of the cluster.

  Table 8. Options to expand storage capacity of the cluster

  Option 1 conditions	Option 2 conditions
  Drive is listed in the Support Matrix Same drive manufacturer Same capacity and endurance Latest model Latest firmware	Drive is listed in the Support Matrix Different drive manufacturer Same capacity and endurance Different model Different firmware

• Ensure that the BIOS, drivers, firmware, and chipset are as listed in the support matrix.
• Apply the BIOS configuration to the node and configure iDRAC. For more information about configuring the node, see Microsoft HCI Solutions from Dell Technologies: End-to-End Deployment with Switchless Networking or Microsoft HCI Solutions from Dell Technologies: End-to-End Deployment with Scalable Networking. Do not run the PowerShell commands in the following sections of the deployment guide again because the cluster is already created, Storage Spaces Direct is already enabled, and the management network is already excluded:
  • Creating the host cluster
  • Enabling Storage Spaces Direct
  • Configuring the host management network as a lower priority network for live migration
• Ensure that the following tasks are completed:
  1. Pass cluster validation and SES device compliance tests.
  2. Verify that the nodes are compliant with the firmware baseline.
  3. Update the hardware timeout configuration for the Spaces port.
  4. After the node configuration, update Microsoft Windows to bring the node to the same level as the cluster.

To manually add server nodes to the cluster, see https://technet.microsoft.com/windows-server-docs/storage/storage-spaces/add-nodes.

In an HCI cluster, expanding storage by adding drives on the available slots on the cluster nodes adds storage capacity to the cluster and improves storage performance. Before the storage expansion, ensure that all disk types and the amount in each node are the same and are equal to that of the node in use. Do not combine two different disk types in the same cluster or node. For example, you cannot combine SATA and SAS HDD/SSD drives in the same node or cluster.

The following options for expanding the storage capacity of the cluster are supported:

• Option 1: Expand the storage with the same drive manufacturer, capacity, endurance, latest model, and latest firmware. Determine if it is available on the AX node support matrix.
• Option 2: Expand the storage with a different drive manufacturer, model, firmware, and the same capacity and endurance. Determine if it is available on the AX node support matrix.

When new disks are added to extend the overall storage capacity per node, the Azure Stack HCI cluster starts claiming the physical disks into an existing storage pool.

After the drives are added, they are shown as available for pooling (CanPool set to True) in the output of the Get-PhysicalDisk command.

Within a few minutes, the newly added disks are claimed in the existing pool and Storage Spaces Direct starts the rebalance job. Run the following command to verify that the new disks are a part of the existing pool:

PS C:\> Get-StorageSubSystem -FriendlyName *Cluster* | Get-StorageHealthReport
CPUUsageAverage                 :   2.66 %
CapacityPhysicalPooledAvailable :   8.01 TB
CapacityPhysicalPooledTotal     :  69.86 TB
CapacityPhysicalTotal           :  69.86 TB
CapacityPhysicalUnpooled        :      0 B
CapacityVolumesAvailable        :  15.09 TB
CapacityVolumesTotal            :  16.88 TB
IOLatencyAverage                : 908.13 us
IOLatencyRead                   :      0 ns
IOLatencyWrite                  : 908.13 us
IOPSRead                        :      0 /S
IOPSTotal                       :      1 /S
IOPSWrite                       :      1 /S
IOThroughputRead                :      0 B/S
IOThroughputTotal               :  11.98 KB/S
IOThroughputWrite               :  11.98 KB/S
MemoryAvailable                 : 472.87 GB
MemoryTotal                     :    768 GB

After all available disks are claimed in the storage pool, the CapacityPhysicalUnpooled is 0 B.

The storage rebalance job might take a few minutes. You can monitor the process by using the Get-StorageJob cmdlet.