Openstack租户下的分区帐户/用户

We have a J2EE based multi-tenant SaaS application running on Tomact-Oracle stack. We are in the process of migrating this application to Openstack based cloud (rackspace). We would like to give our big customers dedicated resources like nodes, volumes etc, while smaller customers might share resources. How do we achieve this partitioning? As I understand, we will be a tenant/project in the Openstack. Should we create each of our customer as a user under Openstack project and allocate resources accordingly? Should we allocate different network partition for each customer? I am thinking that this approach is Operations intensive.We have a J2EE based multi-tenant SaaS applicat