Enable TRIM/UNMAP from Nested vSAN OSA/ESA to physical vSAN OSA

If you are running Nested vSAN Original Storage Architecture (OSA) or vSAN Express Storage Architecture (ESA) workloads on top of a physical vSAN OSA setup, you may want to enable the Guest TRIM/UNAMP capability, which would allow your the "inner" (Nested) workloads to pass the TRIM/UNMAP requests down into your physical vSAN OSA deployment for space reclamation.

It was recently observed that storage utilization may continue to increase on a physical vSAN OSA setup even when the Nested vSAN ESA/OSA workloads have already freed up their storage, which is due to the fact that the TRIM/UNAMP commands are not being passed down into the physical vSAN OSA. If you are using vSAN ESA for your physical setup, Guest TRIM/UNMAP is already enabled by default, so this is only applicable if you are using vSAN OSA.

To enable the Guest TRIM/UNMAP capability, you need apply the following ESXi Advanced Setting to your physical vSAN OSA.

You can use ESXCLI (locally or remotely) by running the following command:

esxcli system settings advanced set -o /VSAN/GuestUnmap -i 1

You can also use PowerCLI by running the following command:

Get-VMHost | Get-AdvancedSetting -Name VSAN.GuestUnmap | Set-AdvancedSetting -Value 1 -Confirm:$false

Once the configuration change has been applied to your ESXi hosts, you will need to perform a power cycle of all vSAN OSA/ESA workloads including the Nested ESXi VMs for the change to go into effect.