The total number of available PCIe slots depends directly on the number of CMIOUs in the PDomain. Each CMIOU has three PCIe slots. Each PDomain must have at least one network adapter, and most configurations require at least one storage adapter.
You can assign an I/O device or a virtual function to a guest domain, making it an I/O domain, or you can assign an entire PCIe bus to a guest domain, making it a non-primary root domain (NPRD) that provides virtualized I/O services to other guest domains. You can also run applications in NPRDs to achieve bare-metal performance.
The number of possible I/O domains is proportional to the number of devices and virtual functions that are available to the PDomain. The number of NPRDs is directly dependent on the number of available root complexes. You can use single root I/O virtualization (SR-IOV) to create virtual functions to increase the number of I/O domains. See I/O Domains With SR-IOV Configuration for an example of a basic configuration that uses SR-IOV to increase the number of I/O domains that can exist in a PDomain. See Virtualization Guidelines and Restrictions for more information about I/O domains, and Bare Metal Plus Zones Configuration for more information about NPRDs.
The following table lists the number of available slots per PDomain on each server, minus the slot that is required for the network adapter, along with the number of available slots if a storage adapter is installed. The number of possible NPRDs that own a root complex to provide virtualized I/O to guest domains is directly proportional to the number of available PCIe slots.