A number of VMFS datastores report 0 bytes capacity in vSphere Client when selecting view: Host and clusters - [host] - Datatstores.
The datastores appear accessible and VMs continue to run normally.
VMware vSphere ESXi (all versions)
VMware vCenter Server (all versions)
On one or more ESXi hosts, there is a failure to initialize ATS locking on an ATS-only device. Hence the datastore fails to mount and is inaccessible on those hosts.
vCenter poplulates datsatores information in the vSphere Client by querying this information from the ESXi hosts. If the vCenter queries a host on which these datastores have failed to mount due to failure to initialize ATS locking, the ESXi will return a value of zero for datastore capacity to vCenter.
Resolve the "Failed to initialize VMFS distributed locking on volume" on datastores.
See:
Datastore mount operation fails with the error "This host does not support ATS, or ATS initialization"
Datastore fails to mount with "Failed to initialize VMFS distributed locking on volume...Not Supported" - due to missing claim rules