Now let’s say, these VMs normally use only 2.5GB of RAM but sometimes they peak to 4GB. Without any memory overcommit I can load this host with 12 VMs of each 4GB. I now start loading it with VMs that have 4GB RAM assigned.

Host has 48GB of RAM and just for the sake of argument we’ll pretend the hypervisor doesn’t use any RAM and we don’t have memory overhead per VM. Good memory overcommit: When you assign more RAM to your VMs than available in your host BUT never cross the line where the amount of RAM that is USED by your VMs is more than available in your host.īad memory overcommit: When you assign more RAM to your VMs than available in your host AND cross the line where the amount of RAM that is USED by your VMs is more than available in your host. In short: When you assign more RAM to your VMs than available in your host. What struck me in this was that on a subject like this, there is so much misunderstanding although there is a lot of documentation available that can explain the subtle difference between good and bad overcommit of memory. There was a good discussion on twitter on memory overcommit and the value of memory overcommit and whether you should or should not use it in production.

What to do when multibeast frees in vm