If you want I/O Domains set up on your Oracle SuperCluster, either at the time of the initial installation or afterwards, you must have at least one Root Domain set up at the time of the initial installation. I/O Domains can then be created from the Root Domains.
A certain number of CPU cores are always reserved for each Root Domain, depending on which domain is being used as a Root Domain and the number of IB HCAs and 10GbE NICs that are associated with that Root Domain:
The last domain in a domain configuration:
Two cores reserved for a Root Domain with one IB HCA and 10GbE NIC
Four cores reserved for a Root Domain with two IB HCAs and 10GbE NICs
Any other domain in a domain configuration:
One core reserved for a Root Domain with one IB HCA and 10GbE NIC
Two cores reserved for a Root Domain with two IB HCAs and 10GbE NICs
All remaining Root Domain CPU cores are parked in the CPU repository, and can be allocated to I/O Domains.
The CPU repository contains resources not only from the Root Domains, but also any parked resources from the dedicated domains. Whether the CPU core resources originated from dedicated domains or from Root Domains, once those resources have been parked in the CPU repository, those resources are no longer associated with their originating domain. These resources can also be allocated to I/O Domains.
In addition, the CPU repository contains parked resources only from the compute server that contains the domains providing those parked resources. In other words, if you have two compute servers and both compute servers have Root Domains, there are two sets of CPU repositories, where each compute server has its own CPU repository with parked resources.
For more information about parked resources, see Root Domains and I/O Domains.
For more information about planning I/O Domain resource allocations, refer to the Oracle I/O Domain Administration Guide.