As of Harvester release v1.2.0, single-node clusters are supported for implementations that require minimal initial deployment resources or that can tolerate lower resiliency. You can create single-node clusters using the standard installation methods (ISO, USB, and PXE boot).
Single-node clusters support most Harvester features, including the creation of RKE2 clusters and node upgrades (with some limitations). However, this deployment type has the following key disadvantages:
- No high availability: Errors and updates that require rebooting of the node cause downtime to running VMs.
- No multi-replica support: Only one replica is created for each volume in Longhorn.
- No live migration and zero-downtime support during upgrades.
Before you begin deploying your single-node cluster, ensure that the following requirements are addressed.
Hardware: Use server-class hardware with sufficient resources to run Harvester and a production workload. Laptops and nested virtualization are not supported.
Network: Configure ports based on the type of traffic to be transmitted among VMs.
StorageClass: Create a new default StorageClass with the Number of Replicas parameter set to "1". This ensures that only one replica is created for each volume in Longhorn.important
The default StorageClass
harvester-longhornhas a replica count value of
3for high availability. If you use this StorageClass to create volumes for your single-node cluster, Longhorn is unable to create the configured number of replicas. This results in volumes being marked as "Degraded" on the Longhorn UI.