Cluster failover scenarios on your Azure Stack Edge Pro GPU device
This article identifies the common failover scenarios, how the Azure Stack Edge device responds, and the overall impact on the workloads deployed on the cluster should a failover occur.
About failover
Azure Stack Edge can be set up as a single standalone device or a two-node cluster. In a two-node cluster, the clustered nodes provide high availability for applications and services that are running on the cluster.
If one of the clustered node fails, the other node begins to provide service - this process is known as failover. Failover may also occur if hardware components associated with one or both nodes of your device such as disk drives, power supply units (PSUs), or network fail or when you update your device nodes.
Failover scenarios
Failover may occur as a result of hardware component failure, node failure or when updating the Azure Stack Edge cluster.
Hardware failures
These tables summarize the failure scenarios for a physical hardware component associated with your device cluster such as one or more of disk drives, power supply, or network.
Disk drive failures
| Node A | Node B | Cluster survives | Failover | Details |
|---|---|---|---|---|
| 1 disk drive fails | No failures | Yes | No | Cluster is degraded until the disk is replaced. |
| 2 or more disk drives fail | No failures | Yes | No | Cluster is degraded until the disk is replaced. |
| 1 or more disk drives fail | 1 or more disk drives fail | No | Cluster goes offline. |
Power supply unit failures
| Node A | Node B | Cluster survives | Failover | Details |
|---|---|---|---|---|
| 1 PSU fails | No failures | Yes | No | Another power supply failure on node A will result in failover to node B. |
| 1 PSU fails | 1 PSU fails | Yes | No | Another power supply failure on either node will result in failover. |
| 2 PSUs fail | No failures | Yes | Yes | VMs on node A fail over to node B. |
| 2 PSUs fail (TBC) | 1 PSU fails | Yes | Yes | VMs on node A fail over to node B. |
| 2 PSUs fail | 2 PSUs fail | No | Cluster goes offline. |
Network failures
| Node A | Node B | Cluster survives | Failover | Details |
|---|---|---|---|---|
| Port 1, Port 2, Port 5, or Port 6 fails | No failures | Yes | No | Failed port is unavailable. Apps listening on this port are impacted |
| 1 or both of Port 3 and Port 4 fail | No failures | Yes | Yes | VMs on node A fail over to node B |
Node failures and updates
Node failure
This table summarizes the failure scenarios when an entire node has failed on your cluster.
| Node A | Node B | Cluster survives | Failover | Details |
|---|---|---|---|---|
| Entire node fails | No failures | Yes | Yes | VMs from node A fail over to node B |
| Entire node fails | Entire node fails | No | - | Cluster goes offline |
| Reboot | No failures | Yes | Yes | VMs from node A fail over to node B |
| Reboot | Reboot | No | - | Cluster is offline until the reboot completes |
| Core component fails. For example, motherboard, DIMM, and OS disk. | No failures | Yes | Yes | VMs from node A fail over to node B |
| Core component fails. For example, motherboard, DIMM, and OS disk. | Core component fails. For example, motherboard, DIMM, and OS disk. | No | - | Cluster goes offline |
Node update
| Node A | Node B | Cluster survives | Failover | Details |
|---|---|---|---|---|
| Node update | No failures | Yes | Yes | VMs from node A fail over to node B |
| Node update | 2 PSUs fail | No | - | Cluster goes offline |
| Node update | Entire node fails or goes offline | No | - | Cluster goes offline |
| Node update | Reboot | No | - | Cluster goes offline |
| Node update | Core component fails such as motherboard, DIMM, and OS disk. | No | - | Cluster goes offline |
Next steps
- Learn about VM sizes and types for Azure Stack Edge Pro GPU.