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This article provides the requirements and supported configurations for rack aware clusters.
General requirements
| Category | Details |
|---|---|
| System requirements | All Azure Local system requirements apply to rack aware clusters. See System requirements for Azure Local. |
| Drive requirements | Data drives must be all-flash. Either Nonvolatile Memory Express (NVMe) or solid-state drives (SSD) work. |
| Availability zones | - Supports two local zones with maximum four machines per zone. - The two zones must contain an equal number of machines. - A machine can belong to only one zone. |
| Deployment type | Only new deployments are supported. Conversion from standard clusters deployments to rack aware clusters isn't supported. |
| Latency requirement | Round-trip latency between racks must be 1 millisecond or less. |
| Bandwidth requirement | Dedicated storage network is required for synchronous replication between racks. For details on bandwidth requirements based on cluster size and network interface card (NIC) speed, see Bandwidth requirements. |
Bandwidth requirements
The necessary bandwidth can be calculated based on the cluster size and the network interface card (NIC) speed, as described in the following table:
| Machines per zone | NIC speed (GbE) | Storage ports per machine | Total bandwidth required (Gbps) |
|---|---|---|---|
| 1 | 10 GbE | 2 | 20 Gbps |
| 2 | 10 GbE | 2 | 40 Gbps |
| 3 | 10 GbE | 2 | 60 Gbps |
| 4 | 10 GbE | 2 | 80 Gbps |
| ➖ | ➖ | ➖ | ➖ |
| 1 | 25 GbE | 2 | 50 Gbps |
| 2 | 25 GbE | 2 | 100 Gbps |
| 3 | 25 GbE | 2 | 150 Gbps |
| 4 | 25 GbE | 2 | 200 Gbps |
Supported node configurations
The following table summarizes the supported configurations with volume resiliency settings:
| Number of machines in two zones | Workload volumes | Volume resiliency | Storage efficiency | Fault tolerance |
|---|---|---|---|---|
| 1+1 (2-node cluster) | 2 | Two-way mirror | 50% | Single fault (drive, node, or rack) |
| 2+2 (4-node) | 4 | Four-way mirror | 25% | Three faults (drive or node). If one rack fails, the remaining can sustain one fault of drive or node. |
| 3+3 (6-node) | 6 | Four-way mirror | 25% | Three faults (drive or node). If one rack fails, the remaining can sustain one fault of drive or node. |
| 4+4 (8-node) | 8 | Four-way mirror | 25% | Three faults (drive or node). If one rack fails, the remaining can sustain one fault of drive or node. |
Note
- Rack Level Nested Mirror (RLNM) is required for all configurations.
- You can’t create 3-way mirror volumes. Only 2-way or 4-way mirror volumes are supported.
Key considerations
Keep in mind the following key considerations for rack aware cluster:
- You can deploy rack aware clusters through the Azure portal or using ARM template.
- You can create Azure Local VMs and assign them to specific zones to balance workloads. Based on VM criticality, you can configure:
- Strict placement. VM stays in its assigned zone and doesn't fail over.
- Non-strict placement. VM can fail over to the other zone if needed.
- You can scale the cluster by adding a pair of nodes to a rack aware cluster. The 2+2 configuration can be expanded to 3+3, and 3+3 to 4+4. However, adding nodes to a 1+1 rack aware cluster isn't supported in this release.
Recommendations
Perform load testing to ensure the solution is properly scaled for production.
Conduct live migration and failover testing for VM workloads.
During planned failovers, non-strict VMs are seamlessly migrated to operational nodes within the same zone or, if necessary, to another zone with no downtime.
During unplanned failovers, VM operations might be interrupted. Typically, systems require three to five minutes to restore availability on an alternate node or zone.
The following table outlines the VM placement and failover behavior:
VM starting placement Failure mode VM placement reaction Recovery VM placement after recovery Zone 1 (strict) Zone 1 down Saved mode (no failover) Zone 1 back Zone 1 (strict) Zone 1 (non-strict) Zone 1 down Zone 2 (non-strict) (failover) Zone 1 back Zone 1 (non-strict) Zone 2 (strict) Zone 1 down No change Zone 1 back No change Zone 2 (non-strict) Zone 1 down No change Zone 1 back No change
When reporting issues, collect diagnostic logs. See Collect diagnostic logs for Azure Local.
Unsupported configurations
- Applying VM affinity rules using Windows Admin Center and PowerShell can result in unknown behavior.
- Adding nodes to a 1+1 rack aware cluster isn't supported in this release.
Next steps
This feature is available in Azure Local 2510 and later.