ESXi 6.5 - Guest Mem% doesnt match with Guest Resource Monitor memmory usage inside VMs

Question

I have strange issue with ESXi Host : in preview of VM, it shows not valid Memmory usage informations when compared to Resource monitor inside Guest OS, as example : VM name Assigned memory / ESXi Guest Mem % vs Guest Resource usage : VM1 4Gb / 8% vs 54% VM2 128GB / 6% vs 16% VM3 24GB / 12% vs 46% Is there a way how to show these real Guest OS memory informations in ESXi host? Having such bad information in ESXI has 0 value.....(Who knows if the other usage statistics are proper and valid then) (Data are read through vCenter 7, but have to say, that the values are same on host directly too) Thank you

Answer 1

This is very badly formatted so there's a chance I've misunderstood your question but if it's about how there's a difference between what the VM says the memory usage is and what vCenter/ESXi says it is then that's fully expected.

This is actually very basic ESXi knowledge but unlike other hypervisors ESXi has a fantastic memory trick in that if you ask for say an 8GB VM then when the VM is powered on ESXi doesn't allocate ANY memory until it's actually requested/used. This means that if that VM only ever uses say 4GB then that's all that is stored - you can think of it as memory-on-demand. There's no real performance impact because of this but it does allow for a larger number of VMs to run on a host than on most/all other hypervisors. If you really want then you can 'reserve' 100% of the memory and in that case it WILL allocate 100% of the requested VM memory at time of VM start - there's reasons this might be desirable but not too often.

Anyway hope this help, maybe get some ESXi training if you can.