By this error, Troubleshooter reports that VM and Host performances are highly degraded because of high memory ballooning.

Virtual memory ballooning is a computer memory reclamation technique used by a hypervisor to allow the physical host system to retrieve unused memory from certain guest virtual machines (VMs) and share it with Others.

So host physical memory is reclaimed based on four “free memory states”, each with a corresponding threshold. Based on the Threshold, the VMkernel chooses which reclamation technique it will use to reclaim memory from virtual machines as explained in this vmware White paper.

When memory reclamation exceeds the 5% limit, memory ballooning leads to an high degradation of host performance.

Further information can be retrieved in this article.


If the host has little free memory available, and if you notice a degradation in performance, consider taking the following actions

  • Verify that VMware Tools is installed on each virtual machine. The balloon driver is installed with VMware Tools and is critical to performance.
  • Verify that the balloon driver is enabled. The VMkernel regularly reclaims unused virtual machine memory by ballooning and swapping. Generally, this does not impact virtual machine performance.
  • Reduce the memory space on the virtual machine, and correct the cache size if it is too large. This frees up memory for other virtual machines.
  • If the memory reservation of the virtual machine is set to a value much higher than its active memory, decrease the reservation setting so that the VMkernel can reclaim the idle memory for other virtual machines on the host.
  • Migrate one or more virtual machines to a host in a DRS cluster.
  • Add physical memory to the host.

Read also the following section of VMware manual.


Posted in: VMware vSphere