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Another thread on an internal DL at NetApp brought up problems clearing stale .lck files. .lck files are lock files used by ESX/ESXi on NFS datastores to prevent multiple hosts from attempting to run the same VM or VMs that share VMDK files. Usually, vCenter does a good job of keeping track of what is running on which ESX(i) host, but if you have multiple instances of vCenter sharing a datastore or a host gets isolated from other hosts and vCenter due to a network issue, .lck files are the last defense against “split brain” in which 2 or more ESX(i) servers, unaware of each other, attempt to start the same VM which is almost guaranteed to cause some form of corruption in the VM.
Read more at: Some quick notes on VMware NFS .lck files