Unable to hot-add memory to a VMware virtual machine

Solution Unverified - Updated -

Environment

  • Red Hat Enterprise Linux
  • VMware

Issue

  • Hot plug memory is not being added to the system.

Resolution

  • Increase the VM's memory to at least the threshold reported in the VMware ESXi log (in this case, 63488 MB or higher).

Root Cause

  • The requested memory increase did not meet VMware's minimum threshold required to trigger a hot-add event. VMware only performs hot-add when the new memory value meets or exceeds the internally required minimum increment.

Diagnostic Steps

  • The following messages are observed in the VMware ESXi logs when hot-add fails:
vmx - memoryHotplug: Change of memory size from 59392 to 61440 was requested
vmx - memoryHotplug: Please increase guest size to at least 63488MB to trigger hotplug event
  • This indicates that the memory increase (59392 -> 61440 MB) was below the required threshold (≥63488 MB) for hot-add to be applied.

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