$ 0 0 For clustering Thick Provision is mandatory and Eager Zeroed is adviced. Differences between them are explained here: http://pubs.vmware.com/vsphere-50/index.jsp?topic=%2Fcom.vmware.vsphere.vm_admin.doc_50%2FGUID-4C0F4D73-82F2-4B81-8AA7-1DD752A8A5AC.html