First and foremost thank you for this great tool, but I do have a few questions with the results.
I’m really slamming my head against the desk on this one, I’ve read tons of articles about this, but none quite get me there. Can anyone please debunk this once and for all for me?
We’re attempting to overcommit memory in our 2 host cluster, call it HOST01 and HOST02.
Our hosts have 256GB physical memory available, and one of our hosts(HOST02) has over 96% of physical memory “allocated” to the running VMs. However, the amount of ACTIVE physical memory these VMs are using is VERY low in the < 20GB range.
We wanted to test over commitment and see what happened hoping the "memory states" of High Low Hard etc, were based on the amount of active physical memory actually being used.
Once we vMotioned 10 or so VMs to HOST2 and got it over 100% allocated, esxtop, 'm' started blowing up in SWAP /MB, ZIP /MB and MEMCTL/MB, I saw it go from high to soft to hard and back to high. VMs we're also showing active swapping etc.
We've since balanced the cluster back out where the memory allocated is around 70% and it appears some items are still going through memory reclaim techniques.
I haven't been able to find a definitive answer on the memory reclaim techniques, based off what I am seeing, it's almost as if VMware is oblivious to the amount of Active Physical memory being used by the virtual machines running on the host.
Once the PMEM /MB value gets below a certain % of what seems to be ALLOCATED memory to VMs it appears the memory state flips, and memory reclaim techniques kick in and start swapping, compressing, ballooning etc. Why would it do this is the host truly has plenty of physical memory available for use?
Am I missing something? This seems inefficient, why if I have 256 Physical Memory can't I allocate say 500GB of memory to my VMs if my VMs are only truly using 20GB physical memory? I should be able to allocate as much as I want to the point of exhaustion where minimal physical memory is available THEN start memory reclaim techniques.
