Logical partitions

A logical partition (LPAR) is the division of a computer's processors, memory, and hardware resources into multiple environments so that each environment can be operated independently with its own operating system and applications.

The number of logical partitions that can be created depends on the system's processor model and resources available. Typically, partitions are used for different purposes, such as database operation, client/server operations, Web server operations, test environments, and production environments. Each partition can communicate with the other partitions as if each partition is a separate machine.

The AIX® operating system supports partitioned environments. Although the AIX installation concepts are the same, the configuration and management of a partitioned environment with the AIX operating system are new.

A logical partition must contain a minimum set of resources, as follows:
  • 1 GB of available system memory
  • One available system processor
  • One boot device on an assigned I/O slot
  • One available network adapter (for error reporting)
  • Any other adapters you might need on an assigned I/O slot

Processors, memory, and I/O slots can be allocated to any partition, regardless of their location. However, if you attempt to activate a partition, but the resources you specified are not available at the time, partition activation fails. It is important to keep track of your system's resources to avoid activation failures. PCI slots are assigned individually to partitions, and memory can be allocated in 256 MB increments. The granularity of the resources that can be assigned to partitions is very fine, providing flexibility to create systems with just the desired amount of resources. Each partition runs its own copy of the AIX operating system and is isolated from any activity in other partitions. Software failures do not propagate through the system, and the hardware facilities and microcode isolate the resources.