I helped a customer upgrading from VCF 4.3 to 4.4 and encountered the following error message during the Upgrade Precheck:
“ESXi Temporary Directory Exist”
Expanding the error message gave me the following error description with several remediation suggestions:
“Directory /locker on host does not support the upgrade for resource, Please check”

None of the suggestions worked, so I started investigating log files and found that the ESXi hosts had an inaccessible Datastore which the customer’s backup solution had left behind after a failed backup job. Unmounting the Datastore from the hosts resolved the issue.