VMware vCLS datastore selection

Recently I noticed that after updating a VMware vCenter from 6.7 to 7.0 u1 the new VMware vCLS VMs where placed on datastores that are not meant for VMs.

Starting with vSphere 7.0 Update 1, vSphere Cluster Services (vCLS) is enabled by default and runs in all vSphere clusters.
vCLS ensures that if vCenter Server becomes unavailable, cluster services remain available to maintain the resources and health of the workloads that run in the clusters.

The datastore for vCLS VMs is automatically selected based on ranking all the datastores connected to the hosts inside the cluster. A datastore is more likely to be selected if there are hosts in the cluster with free reserved DRS slots connected to the datastore. The algorithm tries to place vCLS VMs in a shared datastore if possible before selecting a local datastore. A datastore with more free space is preferred and the algorithm tries not to place more than one vCLS VM on the same datastore. You can only change the datastore of vCLS VMs after they are deployed and powered on.

You can perform a storage vMotion to migrate vCLS VMs to a different datastore.

If you want to move vCLS VMs to a different datastore or attach a different storage policy, you can reconfigure vCLS VMs. A warning message is displayed when you perform this operation.

Conclusion: If datastores used that are intended for e.g. repository purposes, it is possible that the vCLS files are placed on that datastores. You can tag vCLS VMs or attach custom attributes if you want to group them separately.

Reference: docs.vmware.com

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