ESXi host log messages split into multiple lines in vmkernel and vmkwarning logs

Products

• VMware vSphere ESXi

Issue/Introduction

ESXi host log messages in vmkernel.log and vmkwarning.log are truncated and split into multiple lines when the message length is extensive. This behavior specifically impacts the readability of storage performance warnings (e.g., StorageDeviceIO latency alerts) and prevents proper log aggregation and latency alert configuration in Aria Operations for Logs (formerly vRLI).

Example of a split log entry(/var/run/log/vmkwarning.log):

Wa(180) vmkwarning: cpu0:######)WARNING: StorageDeviceIO: 201: Device <DEVICE_NAME> performance has deteriorated. I/O latency increased from average value of ## microseconds to
Wa(180) vmkwarning: cpu0:######)WARNING: ###### microseconds.

Environment

VMware ESXi 7.x

VMware ESXi 8.x

Cause

This is an expected architectural limitation within the ESXi logging framework. The internal vmkernel logging buffer has a hard-coded constraint of 256 characters per entry. Any single log message exceeding this character count is automatically wrapped to a subsequent line by the syslogger to manage kernel memory consumption.

Resolution

There is currently no configuration change, advanced setting, or workaround available to address this behavior.

If you notice this behavior, we recommend you to submit a feature request.