In computing, a Logical Partition, commonly called an LPAR, is a subset of computer's hardware resources, virtualized as a separate computer. In effect, a physical machine can be partitioned into multiple LPARs, each housing a separate operating system. LPAR designates the logical partitioning function and mode of operation in which hardware resources are shared between partitions.

Logical partitioning (LPAR) on IBM servers, which began (on IBM mainframes) with a predominantly physical partitioning scheme based on hardware boundaries, has now evolved into one that allows for virtual and shared resources with dynamic load balancing (i.e., the IBM pSeries Server).

The latest IBM p5 and OpenPower extends the capabilities of the IBM pSeries server by introducing flexibility in partition usage. There are now two types of partitions in the IBM p5 and OpenPower. Partitions can have dedicated processors, or they can have virtualized processors from a single pool of shared physical processors. Both types of partitions can coexist at the same time in the same system.

Sharing a pool of virtualized processors is known as Micro-Partitioning technology. In the IBM pSeries servers, this technology is implemented via the Virtual I/O Server - this is a special-purpose partition that provides virtual I/O resources to client partitions. The Virtual I/O Server owns the real resources that are shared with other clients. With Virtual I/O technology, you can assign a physical adapter to a partition to be shared by one or more partitions, enabling clients to minimize their number of physical adapters. Ethernet and SCSI I/O devices also have been virtualized enabling these resources to be shared by multiple partitions.

To configure and operate these partitions, IBM provides the Hardware Management Console (HMC). Using an HMC, the following tasks can be performed:

  • Configure and manage logical partitions and partition profiles
  • Non-disruptively move memory, CPU capacity, and I/O interfaces between LPARs within the same server - i.e., perform dlpar functions.
  • Activate and manage dormant processor and memory resources within your system, without taking your system or application down - i.e., activate and manage Capacity on Demand resources.

While on one hand, this mix of partitioning technologies (dedicated and shared) facilitates more efficient resource usage, on the other hand, it serves as a catalyst for the creation of a large number of partitions with smaller resource allocations, thereby increasing the size and complexity of the virtualized environment, and consequently, compounding the monitoring and management troubles of administrators. Administrators therefore need a single, central solution that can look across the multitude of LPARs configured on a pSeries server, accurately identify the LPAR that is experiencing a slowdown, and automatically lead you to the root-cause of such slowdowns. This is where eG Enterprise comes as a great solution to administrators.