To run successfully, your host must have a diagnostic partition or a dump partition to store core dumps for debugging and technical support.

Typically, a local diagnostic partition is created during ESXi installation. You can override this default behavior if, for example, you use shared storage devices instead of local storage. To prevent automatic disk formatting, detach the local storage devices from the host before you install ESXi and power on the host for the first time. You can later create a diagnostic partition on a local disk or on a private or shared SAN LUN using the client.

The following considerations apply:

A diagnostic partition cannot be located on an iSCSI LUN accessed through the software iSCSI or dependent hardware iSCSI adapter. For more information about diagnostic partitions with iSCSI, see General Boot from iSCSI SAN Recommendations.

Unless you are using diskless servers, set up a diagnostic partition on a local storage.

Each host must have a diagnostic partition of 110MB. If multiple hosts share a diagnostic partition on a SAN LUN, the partition should be large enough to accommodate core dumps of all hosts.

If a host that uses a shared diagnostic partition fails, reboot the host and extract log files immediately after the failure. Otherwise, the second host that fails before you collect the diagnostic data of the first host might not be able to save the core dump.

To mange the host’s diagnostic partition, use the vCLI commands. See vSphere Command-Line Interface Concepts and Examples.