The Compute node is where VM instances are installed. You probably want many compute nodes for your cloud.
To better manage memory use between ZFS and applications in Oracle Solaris 11, set the usr_reserve_hint_pct parameter on the node, as shown in the following example:
# echo "set user_reserve_hint_pct=80" >>/etc/system.d/site:kernel-zones-reserve # reboot
where site can refer to your company.
You should set this parameter on the different OpenStack nodes as well.
For more information about this parameter, log in to your MOS account in https://support.oracle.com and review Document 1663862.1, Memory Management Between ZFS and Applications in Oracle Solaris 11.2.