Insufficient free memory which can lead to NSX upgrade failure. Free up space by migrating VMs or reboot host to defragment.

Products

• VMware NSX

Issue/Introduction

• When attempting to Pre-upgrade checks for NSX-T Host to a version below 4.X, the pre-upgrade validation fails for one or more ESXi hosts. The following error is generated in the NSX Manager UI or upgrade logs:

Pre-upgrade checks failed for HOST: Insufficient free memory which can lead to NSX upgrade failure. Free up space by migrating VMs or reboot host to defragment.

• Checking the #memstats -r buddy-stats from the ESXI Host CLI could see that the minimum 8 MB memory is not meeting:-
  
  

Note: This failure occurs even when the Host Upgrade Mode is configured to Maintenance Mode, where some/no virtual machines are active on the host.

Environment

• VMware NSX-T Data Center

Cause

• During the NSX VIB upgrade process to versions 3.2.1, 3.2.4, the Upgrade Coordinator enforces a restrictive NUMA-aware memory validation. This pre-check requires a minimum of 8 MB of contiguous free memory on every individual NUMA node. Even if the aggregate physical memory on the host is sufficient, the pre-check will trigger a failure if any single NUMA node fails to meet this specific local threshold.

Resolution

• This has been fixed in 4.X and later, if the upgrade mode is set to "Maintenance", the error will be skipped and the upgrade will continue even if an error occurs.
• To avoid the error, free up memory by powering off or vmotion the virtual machine.