PCIe I/O card slots are divided into three levels of performance. These levels are first tier, second tier, and third tier, as defined below.
First tier slots have dedicated resources and provide the best performance. Install high-bandwidth cards in the first tier slots shown below.
Second tier slots share resources with other server components, so the throughput performance of these slots can be affected. Use second tier slots after the first tier slots are filled.
Third tier slots share resources with the EMS modules and their subordinate components. Use these slots after first and second tier slots are filled.
The table notes in italic font two slots where I/O card slot performance differs between fully-populated and half-populated DCUs. Footnotes mark additional slots where performance can be affected when a PDomain restarts. See the following notes for more information.
Note - PCIe I/O card slot performance can change if the I/O paths are reconfigured when the PDomain is reset, as can occur when an I/O card is removed or added. The Oracle ILOM property /HOSTx/ioreconfigure controls this reconfiguration behavior. To change the setting for ioreconfigure, refer to Server Administration, manage I/O path reconfiguration settings.
Note - Half-populated DCU: The DCU configuration described here is the factory default, which has CMUs in the first and fourth CMU slots, and EMSs in IOU slot numbers EMS1 and EMS3. Other half-populated configurations are possible but can have limitations. See CMU Configuration.
For more information about hard disk and SSD device paths and root complexes, refer to Server Administration, understanding hard drive device paths.