# Storage-only nodes

A storage-only node, also known as storage node, is a VMware Engine
node type that does not have any customer-usable cores and only has
customer-usable storage. These nodes can be added to a cluster of
VMware Engine hyper converged nodes to increase the storage capacity of
the cluster without adding cores to the cluster.

> [!NOTE]
> **Note:** A cluster can consist of a maximum of **50%** storage-only nodes. A dedicated cluster made up entirely of storage-only nodes is not supported because the workload VMs can't run on storage-only nodes.

Storage-only nodes can only be added to a management cluster with a minimum of
three HCI nodes and a workload cluster that has at least two HCI nodes.

Storage-only nodes are available using the Google Cloud console, Google Cloud CLI and
VMware Engine API. The storage nodes don't contribute cores or memory to the
private cloud and cluster and can't run VMs. You can use the Google Cloud CLI and
VMware Engine API to query the number of storage-only nodes in a cluster.

By accessing the vCenter UI, you can identify which ESXi hosts are configured as
storage-only nodes by looking at tags assigned to ESXi hosts. You can query for
the tag `storage_only_node` in vCenter and find all ESXi hosts that
have this tag.

## Limitations

- When using a cluster made up of two HCI and one storage node, if there's an
  HCI node failure, there might be only one available HCI node in the cluster
  to run VMs. This scenario can remain until the cluster adds a replacement
  node, at which time your cluster is restored back to resilience.

- You won't be able to use vMotion on a VM to a storage node within a cluster.
  If you try to perform this action, you may see a vCenter error stating that
  there are insufficient resources on the storage node. Instead, you can use
  the vCenter interface to query the "storage-only" tag to find all ESXi hosts
  that are configured as storage nodes.

- Converting a storage node to an HCI node and the other way around is not
  supported.

- When a cluster contains storage-only nodes, the vCenter cluster summary
  reports physical CPU and memory for all nodes of the cluster, including
  compute capacity from storage-only nodes which is unavailable for running
  VMs. For an accurate
  view of available compute resources, use vSphere Distributed Resource
  Scheduler (DRS) stats for CPU and memory utilization. To manually calculate
  available compute resources from cluster summary metrics, exclude compute
  capacity proportional to the percentage of storage-only nodes in your
  vSphere cluster.

## What's next

- Learn how to [use storage only nodes](https://docs.cloud.google.com/vmware-engine/docs/networking/howto-use-storage-only-nodes).