[Rdo-list] Max VM filesystem size?

Hi Y'all, I have a bunch of OpenStack Nova nodes, each with 11TB of local disk for Cloud VMs. This is all on RDO - RHEL 7 on OpenStack Kilo. That local storage is configured with a XFS filesystem. If I specify 8TB on 'root filesystem size' in a flavor, it only seems to be able to make a 2TB root filesystem on the guest. No matter what guest OS I use (I've tried CentOS 7.1, Ubuntu 15.10, others) it only seems to be able to create a 2TB root filesystem. I've also tried making a 5GB root filesystem and specifying 8TB for ephemeral disk, but the ephemeral disk that shows up on /tmp in the guest is only 2TB as well. Is there a 2TB KVM limit on VM size? Max file size in ext4 and XFS is well beyond 2TB, so I don't think that's it... Maybe a limit in KVM or libvirt? The qemu xml file on the node does specify a 8TB disk.... Any insight most welcome!! cheers, erich