Logical partition: Difference between revisions

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On IBM mainframes, LPARs are managed by the [[PR/SM]] facility or a related, optional, simplified facility called Dynamic Partition Manager (DPM). All 64-bit IBM mainframes, except for the first generation 64-bit models (z900 and z800), operate exclusively in LPAR mode, even when there is only one partition on a machine. Multiple LPARs running z/OS can form a [[Sysplex]] or [[IBM Parallel Sysplex|Parallel Sysplex]], whether on one machine or spread across multiple machines.<ref name="redbooks.ibm.com">{{cite web |url=http://www.redbooks.ibm.com/abstracts/sg247803.html |title=Security on the Mainframe |date=2009-12-02 |access-date=2010-01-14 |first=Karan |last=Singh}}</ref>

On IBM [[IBM pSeries|System p]] [[IBM Power Systems|POWER hardware]], LPARs are managed by PHYP (the POWER [[Hypervisor#Unix and Linux servers|Hypervisor]]).<ref>[https://web.archive.org/web/20161017172011/http://www.ibm.com/support/knowledgecenter/POWER6/iphb2/iphb2hypervisor.htm]</ref> PHYP acts as a virtual switch between the LPARs and also handles the virtual [[SCSI]] traffic between LPARs. [[Micro-Partitioning]] supports 10 times as many LPARs as processors with fractional allocations. It was introduced with the [[POWER5]] processor. All IBM [[POWER5]], [[POWER6]], and successor systems may be partitioned. Note that a full system partition may be defined where all resources are consumed by a single partition. System P servers with PowerVM enabled allow LPARs with shared CPUs to delegate their unused cycles into the shared pool. Dedicated processors are not available for sharing. Unused cycles become available for other partitions and are governed by the parameters specified when the LPAR is defined. Changes to a running partition can be made dynamically up to the maximum value set, and down to the minimum value set in the active profile. The changing of resource allocations without restart of the logical partition is called [[Dynamic Logical Partitioning|dynamic logical partitioning]]. IBM PowerVM is the licensed/purchased feature that enables the virtualization features on p4, 5, 6, 7, and subsequent series servers.<ref>{{cite web |url=http://www-01.ibm.com/common/ssi/cgi-bin/ssialias?infotype=an&subtype=ca&appname=Demo&htmlfid=897/ENUS207-269 |title=IBM System p Virtualization — The most complete virtualization offering for UNIX and Linux |date=2007-11-06 |access-date=2010-04-06 |publisher=[[IBM]]}}</ref>

Exploiting [[Intel vPro]] (i.e. [[Non-uniform memory access]]), there are also implementations of Logical Partitioning based on [[Xeon#Haswell-based_Xeonbased Xeon|Intel Xeon]] e.g. by [[Hitachi Data Systems]].<ref name="HDS">{{cite web |url=https://www.hds.com/en-us/pdf/white-paper/hitachi-white-paper-high-performance-nested-virtualization-with-hitachi-lpar.pdf |title=High-Performance Nested Virtualization With Hitachi Logical Partitioning Feature |date=2014-09-01 |access-date=2016-05-29 }}{{Dead link|date=March 2020 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

LPARs (with sufficient certification) safely allow combining multiple test, development, quality assurance, and production work on the same server, offering advantages such as lower costs, faster deployment, and more convenience. IBM mainframe LPARs are Common Criteria [[Evaluation Assurance Level#EAL5: Semiformally Designed and Tested|EAL 5+]] certifiable, equivalent to physically unconnected servers, so they support 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 and later models up to 85.<ref name="redbooks.ibm.com"/>