To autoprovision a node, OneFS requires that the new node be of the same equivalence class as the other nodes in the node pool. OneFS uses the following criteria to determine if the new node is of the same equivalence class:
- Family code
- Chassis code
- Generation code
- Drive configuration
- RAM capacity
If the new node matches all criteria, OneFS provisions the new node to the node pool. All nodes in a node pool are peers, and data is distributed across nodes in the pool. Each provisioned node increases the aggregate disk, cache, CPU, and network capacity of the cluster.
We strongly recommend that you let OneFS handle node provisioning. However, if you have a special requirement or use case, you can move nodes from an autoprovisioned node pool into a node pool that you define manually. The capability to create manually-defined node pools is available only through the OneFS command-line interface, and should be deployed only after consulting with Isilon Technical Support.
If you try to remove a node from a node pool for the purpose of adding it to a manual node pool, and the result would leave fewer than three nodes in the original node pool, the removal fails. When you remove a node from a manually-defined node pool, OneFS attempts to autoprovision the node back into a node pool of the same equivalence class.
If you add fewer than three nodes of an equivalence class to your cluster, OneFS cannot autoprovision these nodes. In these cases, you can often create one or more compatibilities to enable OneFS to provision the newly added nodes to a compatible node pool.
Types of compatibilities include node class, SSD capacity, and SSD count.