After upgrade to ESXi 6.7 U2 and higher, vmkernel reports log spew with errors " Unmap6: 7146: [Unmap] <> Not supported

Products

• VMware vSphere ESXi

Issue/Introduction

To understand the cause of the log spew and to suppress the log spew.

Symptoms:

• After the ESXi host is upgraded to ESXi 6.7 U2 or higher, vmkernel logs reports log spew with errors " Unmap6: 7146: [Unmap] <> Not supported.

• In the vmkernel.log you will see entries similar to

 2019-12-12T20:44:34.145Z cpu11:2134763)J6: 2651: 'Local104': Exiting async journal replay manager world
2019-12-12T20:45:29.148Z cpu21:2099111 opID=12dec6e3)World: 11943: VC opID sps-Main-6419##-##-##-##-##da maps to vmkernel opID 12dec6e3
2019-12-12T20:45:29.148Z cpu21:2099111 opID=12dec6e3)Unmap6: 7146: [Unmap] 'Local104':device(0x43059eabf110)does not support unmap

Note:The preceding log excerpts are only examples.Date,time and environmental variables may vary depending on your environment.

Environment

VMware vSphere ESXi 6.7

Cause

A unmap function checks if the device supports unmap and if it does, it gets optimal unmap granularity and other properties of the device.

 

Resolution

This issue is resolved in ESXi 6.7 P02 build 16075168 or higher.

 

 

Workaround:
If upgrading is not possible then configure log rotation using the below commands
esxcli system syslog config set --default-rotate=30 --default-size=4096
esxcli system syslog reload

For more information refer to VMware KB : Configuring syslog on ESXi

The above settings helps to ensure that other critical logs are not being missed due to log spew.

Additional Information

Impact/Risks:
There is no impact of these errors as they are just informational messages logged in the vmkernel logs for the devices which do not support unmap.