[ovirt-users] Need some help understanding memory allocation

I am a little confused on why my CentOS box is using so much RAM. I currently have a small test setup which only has *12GB* of ram total. When I log into the administrative interface it tells me: *Memory* 4.3 Available of 15.5 GiB Over commit: 39% (allocated 45%) 11.1 GB Used Currently I am only running 3 VMs with memory allocations as follows: Defined Memory: 1024 MB Physical Memory Guaranteed: 1024 MB Defined Memory: 3072 MB Physical Memory Guaranteed: 3072 MB Defined Memory: 2048 MB Physical Memory Guaranteed: 2048 MB *Or 6144MB used by VM* If I SSH into my ovirt host, and run TOP and sort by memory, the top usage items are: 31896 qemu *21.5%* 727:21.44 qemu-kvm 6008 qemu *14.6%* 190:33.70 qemu-kvm 3019 ovirt *13.6%* 35:47.64 java 5800 qemu *8.5%* 784:26.88 qemu-kvm 2565 ovirt *3.9%* 62:58.00 java Everything else is pretty small compared, but for the OVIRT/QEMU we roughly get *Total: 62% = 7.45GB* So I am a bit confused as to the Ram being reported to me by the system (15.5GGB, but the system only has 12GB), and assuming OVIRT is using around 7-8GB, does a bare minimal install of CentOS really need 4-5GB of Ram to run? This is a bare minimal install of CentOS7 running only Webmin and oVirt. I think there are several things I don't understand here, and I am quite new to oVirt and would like to learn, so please excuse my inexperience if this is a silly question! Thanks either way, I am really happy I ditched my ESXi box :D