[ovirt-users] up and running with ovirt 4.2 and gluster

Hi, I have my ovirt 4.2 hci cluster up and running, but I have a probably stupid question. During the setup and in the documents it defaults to setting up the engine datastore/volume, a VMstore/volume and a data/volume. What is the Data volume for? I am planning on running VMs on this so I would assume I need VMstore and that's what I will grow on my system. In previous installs you had the opportunity to create the ISO domain, but not now. I can see how to create in the engine UI so that's fine, but I am just wondering what people use the Data volume for as an example. Thanks Bill