Some quick notes on VMware NFS .lck files

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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.

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Stephen Foskett

Stephen Foskett is an active participant in the world of enterprise information technology, currently focusing on enterprise storage, server virtualization, networking, and cloud computing. He organizes the popular Tech Field Day event series for Gestalt IT and runs Foskett Services. A long-time voice in the storage industry, Stephen has authored numerous articles for industry publications, and is a popular presenter at industry events. He can be found online at,, and on Twitter at @SFoskett.

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