Hi Edward, Are you using Simple.Scheduler? I think it must be related to max_cores option. max_cores default value is 16, you can override it in nova.conf max_cores = 24 cpu_allocation_ratio (vCPU/CPU ratio) default value is 1, if you want to use more virtual cores: cpu_allocation_ratio = ... See: http://docs.openstack.org/trunk/openstack-compute/admin/content/simple.html http://docs.openstack.org/trunk/openstack-compute/admin/content/corefilter.html Alberto