VMkernel Observations (VOBs) are system events that you can use to set up Virtual SAN alarms for monitoring and troubleshooting performance and networking issues in the Virtual SAN cluster. In Virtual SAN, these events are known as observations.

VMware ESXi Observation IDs for Virtual SAN

Each VOB event is associated with an identifier (ID). Before you create a Virtual SAN alarm in the vCenter Server, you must identify an appropriate VOB ID for the Virtual SAN event for which you want to create an alert. You can create alerts in the VMware ESXi Observation Log file ( vobd.log). For example, you should use the following VOB IDs to create alerts for any device failures in the cluster.
  • esx.problem.vob.vsan.lsom.diskerror
  • esx.problem.vob.vsan.pdl.offline

To review the list of VOB IDs for Virtual SAN, open the vobd.log file located on your ESXi host in the /var/log directory. The log file contains the following VOB IDs that you can use for creating Virtual SAN alarms.

Table 1. VOB IDs for Virtual SAN
VOB ID Description


The Virtual SAN clustering service is enabled.


The Virtual SAN device has come online.


The Virtual SAN clustering services is enabled.


Virtual SAN has one active network configuration.


A previously reported vmknic has acquired a valid IP.


Virtual SAN reaches the near node component count limit.


A Virtual SAN device is in a permanent error state.


Virtual SAN fails to create a new disk group.


Virtual SAN fails to add devices to a disk group.

esx.problem.vob.vsan.lsom.diskunhealthy Virtual SAN disk is unhealthy.


A Virtual SAN device is offline.


Virtual SAN clustering services are disabled.


Virtual SAN device memory or SSD congestion has been updated.


A vmknic is added to Virtual SAN network configuration without a valid IP address. This happens when the Virtual SAN network is not ready.


The Virtual SAN network configuration does not have the required redundancy.


Virtual SAN does not have existing networking configuration, which is in use.


A vmknic is added to the Virtual SAN network configuration without a valid IP address.