VMware vSphere 6.5 Host Resources Deep Dive by Frank Denneman & Niels Hagoort

Author:Frank Denneman & Niels Hagoort [Denneman, Frank]
Language: eng
Format: azw3
Published: 2017-07-23T04:00:00+00:00

Figure 160: VM-stats Showing Balloon Target and Ballooned Pages

Unfortunately, there is no method to monitor ballooning activity via API-calls. One popular workaround is to place the guest OS swap file on its own virtual disk and monitor the disk IO.

Java and the Balloon Driver

VMware KB article 1008480 recommends setting the memory reservation equal to the configured memory size of the VM if Java is running inside the VM. The Java VM (JVM) memory is an active heap space in which objects are constantly created and garbage collected. The JVM expects full access to its memory space to operate adequately. As a result, no pages that reside in the JVM heap should be paged out.

Does that mean you should disable the balloon driver? No! Absence of the balloon driver will trigger compression or swapping during memory over commitment, which result in forcibly reclaiming memory. If the host is expected to be over-committed, then it is recommended to set a reservation. No reclamation is done at physical layer if a reservation is set and thus no reclamation technique is initiated for this VM. This recommendation is only valid if memory over commitment is expected. If the hosts in the cluster are under commitment, no reservation is necessary as it affects vSphere High Availability Slot Sizes.

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