File locking mechanisms are used to restrict access to data stored on a server to only one user or process at a time. NFS 3 and NFS 4.1 use incompatible file locking mechanisms.

NFS 3 locking on ESXi does not use the Network Lock Manager (NLM) protocol. Instead, VMware provides its own locking protocol. NFS 3 locks are implemented by creating lock files on the NFS server. Lock files are named .lck-file_id..

NFS 4.1 uses share reservations as a locking mechanism.

Because NFS 3 and NFS 4.1 clients do not use the same locking protocol, you cannot use different NFS versions to mount the same datastore on multiple hosts. Accessing the same virtual disks from two incompatible clients might result in incorrect behavior and cause data corruption.