min_on_demand_count
Description
The min_on_demand_count parameter sets the minimum number of on-demand nodes when using the mixed node capacity type. This allows you to ensure a baseline of on-demand instances in your cluster.
Default Value
The default value for min_on_demand_count is 1.
Use Cases
- Reliability: Ensure that a minimum number of reliable on-demand instances are always available to handle workloads.
- Performance Assurance: Maintain a specific number of on-demand nodes to meet performance and reliability requirements.
Setting Parameters
To set the min_on_demand_count parameter, use the following command:
$ convox rack params set min_on_demand_count=2 -r rackName
Updating parameters... OK
This command sets the minimum number of on-demand nodes to 2.
Additional Information
The min_on_demand_count parameter is used in conjunction with the node_capacity_type parameter. When the node_capacity_type is set to mixed, you can specify the minimum and maximum number of on-demand nodes to balance cost and availability.
Adjusting the min_on_demand_count helps you ensure that there are always a sufficient number of reliable on-demand nodes available for your workloads, complementing the use of spot instances to reduce costs.
Additionally, consider configuring the max_on_demand_count parameter to limit the maximum number of on-demand nodes and optimize resource allocation.
This parameter has no effect when karpenter_enabled is true, because Karpenter holds every system node group at one node. Enabling Karpenter also requires node_capacity_type=ON_DEMAND, so a Karpenter Rack is not a mixed Rack and the two settings do not normally meet. See Karpenter.
On AWS Racks, raising min_on_demand_count above the number of nodes the on-demand node group is currently running requires a convox CLI at 3.25.6 or newer performing the apply. Earlier versions fail the apply with an EKS validation error and roll the value back. Setting the value at install and lowering it work on any version.
This is not a Rack version requirement. The handling lives in the convox binary performing the apply, which for a Console-managed Rack is the CLI bundled in the Console deploy rather than the CLI on your machine. See Raising a node group minimum fails EKS validation and CLI Rack Management.
