Your host must have a diagnostic partition, also referred to as dump partition, to store core dumps for debugging and for use by VMware technical support.

A diagnostic partition is on the local disk where the ESXi software is installed by default. You can also use a diagnostic partition on a remote disk shared between multiple hosts. If you want to use a network diagnostic partition, you can install ESXi Dump Collector and configure the networked partition. See Manage Core Dumps with ESXi Dump Collector.

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 in the vSphere Storage documentation.
  • A standalone host must have a diagnostic partition of 110 MB.
  • If multiple hosts share a diagnostic partition on a SAN LUN, configure a large diagnostic partition that the hosts share.
  • 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.

Diagnostic Partition Creation

You can use the vSphere Web Client to create the diagnostic partition on a local disk or on a private or shared SAN LUN. You cannot use vicfg-dumppart to create the diagnostic partition. The SAN LUN can be set up with FibreChannel or hardware iSCSI. SAN LUNs accessed through a software iSCSI initiator are not supported.

Caution: If two hosts that share a diagnostic partition fail and save core dumps to the same slot, the core dumps might be lost.

If a host that uses a shared diagnostic partition fails, reboot the host and extract log files immediately after the failure.

Diagnostic Partition Management

You can use the vicfg-dumppart or the esxcli system coredump command to query, set, and scan an ESXi system's diagnostic partitions. The vSphere Storage documentation explains how to set up diagnostic partitions with the vSphere Web Client and how to manage diagnostic partitions on a Fibre Channel or hardware iSCSI SAN.

Diagnostic partitions can include, in order of suitability, parallel adapter, block adapter, FC, or hardware iSCSI partitions. Parallel adapter partitions are most suitable and hardware iSCSI partitions the least suitable.

Important: When you list diagnostic partitions, software iSCSI partitions are included. However, SAN LUNs accessed through a software iSCSI initiator are not supported as diagnostic partitions.