I/O device assignment in partition profiles

I/O devices are assigned to partition profiles either on a slot-by-slot basis, or on logical port basis in the case of shared mode single root I/O virtualization (SR-IOV) adapters. For I/O devices that are assigned to partition profiles on a slot-by-slot basis, most I/O devices can be assigned to a partition profile on the HMC as required or as allocated. For SR-IOV logical ports, I/O devices are always assigned to a profile as required.

  • If an I/O device is assigned to a partition profile as required, then the partition profile cannot be successfully activated if the I/O device is unavailable or is in use by another logical partition. Also, after the logical partition starts, you cannot use dynamic partitioning to remove the required I/O device from the running logical partition or move the required I/O device to another logical partition. This setting is suitable for devices that are required for the continuous operation of the logical partition (such as disk drives).
  • If an I/O device is assigned to a partition profile as desired, then the partition profile can be successfully activated if the I/O device is unavailable or is in use by another logical partition. The desired I/O device can also be unconfigured in the operating system or system software and removed from the running logical partition or moved to another logical partition by using dynamic partitioning. This setting is suitable for devices that you want to share among multiple logical partitions (such as optical drives or tape drives).

The exception to this rule is host channel adapters (HCAs), which are added to partition profiles on the HMC as required. Each physical HCA contains a set of 64 globally unique IDs (GUIDs) that can be assigned to partition profiles. You can assign multiple GUIDs to each partition profile, but you can assign only one GUID from each physical HCA to each partition profile. Also, each GUID can be used by only one logical partition at a time. You can create multiple partition profiles with the same GUID, but only one of those partition profiles can be activated at a time.

You can change the required or desired setting within any partition profile for any I/O device at any time. Changes to the required or desired setting for an I/O device take effect immediately, even if the logical partition is running. For example, you want to move a tape device from one running logical partition to another, and the I/O device is required in the active partition profile for the source logical partition. You can access the active partition profile for the source logical partition, set the tape device to be allocated, and then unconfigure and move the tape device to the other logical partition without having to restart either logical partitions.

If you create an IBM® i logical partition by using the HMC, you must tag I/O devices to perform certain functions for that IBM i logical partition.