During a host failure, ESXi must be able to save diagnostic information to a preconfigured location for diagnostic and technical support purposes.
Typically, a partition to collect diagnostic information, also called a core dump, is created on a local storage device during ESXi installation. You can also configure ESXi Dump Collector keep core dumps on a network server. For information on setting up ESXi Dump Collector, see the VMware ESXi Installation and Setup documentation.
Another option is to use a file on a VMFS datastore to collect the diagnostic information.