Version: All openshift versions Platform: oVirt Please specify: IPI What happened? On RHV 4.4.7 the default "guaranteed memory" for a newly created VM was changed. - On RHV < 4.4.7: The guaranteed memory will be taken from the template. - On RHV = 4.4.7: The guaranteed memory will be equal to memory without taking memory Overcommitment into account. - On RHV > 4.4.7: The guaranteed memory will be equal to memory *BUT* with taking memory Overcommitment into account, meaning if you created a VM with 10GB mem and have 150% memory overcommitment set on the cluster level then you will get 10GB*0.66 = 6.6GB of guaranteed memory (See BZ#1993017[1]). For Openshift that change the behavior of the installation, that means that: - On RHV 4.4.7 all the machines will be created with a guaranteed memory equal to memory, which means that if the user relied on having memory overcommitment in RHV to have enough resources Openshift then the installation will fail due to not enough memory. - On RHV 4.4.8 and above (when BZ#1993017[1] is fixed) the VMS will still be created with a guaranteed memory set but at least with a value that makes sense for memory overcommitment - so there is no problem with that. What do we need to do? 1. Document that on RHV 4.4.7 there is a known issue that affects users that rely on memory overcommitment where each VM is created with a guaranteed memory == memory - installation or new machines will not be created if there is not enough *physical memory* in the cluster. 2. Document that on *Openshift 4.9* and above you can set the guaranteed memory on MachineSet as a day2 operation - if you don't set it the behivour is dependent on your RHV version. [1] https://bugzilla.redhat.com/show_bug.cgi?id=1993017