This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (September 2008)

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.

The technology was initially developed separately by Amdahl, Hitachi Data Systems and IBM for the mainframe architecture ESA/390 in the mid 1980s, and continued also for zSeries and System z architectures. However, IBM later extended the idea to non-mainframe, such as pSeries since October 2001 [1] and iSeries, albeit with varying technical specifications. Multiple operating systems are compatible with LPARs, including z/OS, z/VM, z/VSE, z/TPF, AIX, Linux (including Linux on zSeries), and i5/OS. In storage systems, such as the IBM TotalStorage DS8000, LPARs allow for multiple virtual instances of a storage array to exist within a single physical array.

Logical partitioning is performed mostly on the hardware layer. Two LPARs may access memory from a common memory chip, provided that the ranges of addresses directly accessible to each do not overlap. One partition may indirectly control memory of a second partition, but only by commanding a process of the second partition to directly operate on the memory. CPUs may be dedicated to a single LPAR, or shared between separate LPARs. While on Amdahl's MDF it was possible to configure an LPAR with both shared and dedicated CPUs it is no longer possible with mainframes.

On IBM mainframes, LPARs are managed by the PR/SM facility. Modern IBM mainframes operate exclusively in LPAR mode, even when there is only one logical partition on a machine. Multiple LPARs can form a Sysplex or Parallel Sysplex, whether on one machine or spread across multiple machines.

LPARs safely allow combining multiple test, development, quality assurance, and production work on the same system, offering several advantages such as lower costs, faster deployment, and more convenience. IBM mainframe LPARs are Common Criteria EAL5 certifiable, equivalent to physically separate servers with no connections, so they are appropriate for the highest security requirements, including military use. Nearly all IBM mainframes run with multiple LPARs with the IBM System z9 and IBM System z10 supporting up to 60 LPARs.

References

  1. ^ Griffiths, Nigel (2005-06-29). "POWER5 Virtualization: How to set up the Virtual I/O Server". Retrieved on 2008-09-25.

See also

Retrieved from "http://en.wikipedia.org/wiki/LPAR"

No comments have been added.



Your name:

City:

Country:

Your comments:

Security check *
(Please enter the number into adjoining box)