frankdenneman Frank Denneman is the Chief Technologist for AI at VMware by Broadcom. He is an author of the vSphere host and clustering deep dive series, as well as a podcast host for the Unexplored Territory podcast. You can follow him on Twitter @frankdenneman

Gotcha – Disable reserve all guest memory setting does not remove the reservation

38 sec read

A while ago I wrote about the nice feature Reserve all guest memory available in vSphere 5.1 and 5.5. The feature automatically adjusts the memory reservation when the memory configuration changes. Increase the memory size and the memory reservation is automatically increased as well. Reduce the memory size of a virtual machine, and the reservation is immediately reduced.
Setting enabled
This week I received an email from someone who used the settings temporarily and when disabling this setting he was surprised that the reservation was not set to 0, reverting back to the default.

Expected behavior
Expected behavior

Real product behavior
Real product behavior

Although I understand his point of view, the reality is that when you enabled the feature your intent was to apply a memory reservation to the virtual machine. The primary function of this setting is to take away the responsibility of adjusting the reservation when you change the memory reservation.
If your goal is to remove the memory reservation, disable the setting Reserve all guest memory and then change the memory reservation to 0.

frankdenneman Frank Denneman is the Chief Technologist for AI at VMware by Broadcom. He is an author of the vSphere host and clustering deep dive series, as well as a podcast host for the Unexplored Territory podcast. You can follow him on Twitter @frankdenneman

Memory Deep Dive Summary

This is last part of the memory deep dive. As the total series count 7667 words, I thought it would be a good idea...
frankdenneman
4 min read

Memory Deep Dive: NUMA and Data Locality

This is part 6 of the memory deep dive. This is a series of articles that I wrote to share what I learned while...
frankdenneman
7 min read

Memory Deep Dive: DDR4 Memory

This is part 5 of the memory deep dive. This is a series of articles that I wrote to share what I learned while...
frankdenneman
6 min read