Running AIX on a logical partition

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There are several differences between how AIX runs on a logical partition and how it runs on a standalone server.

The following list describes some of these differences:
  • The logical partition resource allocation provides the ability to select individual components to be added to a partition without dependencies between these resources. The slots can be freely allocated in any I/O drawer on the system. Other devices may be required for specific application requirements. It is a good idea to configure more PCI slots in the partition than are required for the number of adapters. This provides flexibility by allowing additional adapters to be hot-plugged into the empty slots that are part of an active partition. Because each partition requires its own separate boot device, the system must have at least one boot device and associated adapter per partition.
  • In order for AIX to run inside a logical partition, AIX calls the Hypervisor in place of its traditional direct access to the hardware and address-mapping facilities.
  • Some direct-access calls are presented for diagnostic purposes, and alternate return codes for Run-Time Abstraction Services (RTAS) calls are used whenever an illegal operation is issued.
  • No physical console exists on the partition. While the physical serial ports on the system can be assigned to the partitions, they can only be in one partition at a time. To provide an output for console messages and also for diagnostic purposes, the firmware implements a virtual tty that is seen by AIX as a standard tty device. Its output is sent to the HMC. The AIX diagnostics subsystems use the virtual tty as the system console.
  • Certain platform operations are constrained in LPARs. For example, in non-LPAR systems, platform firmware updates can be performed from AIX by a root user. Because firmware updates can affect all partitions in an LPAR system, the LPAR administrator can specify that a particular partition (or no partition) has this authority. Within that partition, firmware updates work in the same way as they do for non-LPAR systems.

Apart from these considerations, AIX runs within a partition the same way it runs on a standalone server. No differences are observed either from the application or the administrator's point of view. Third-party applications need only be certified for a level of AIX that runs in a partition, and not for the LPAR environment itself.