logical partition (virtualization) (LPAR)

Logical partitioning (LPAR) is a technique where hardware resources are partitioned, as opposed to virtualization where something is replicated.

Logical partitioning is only available for mainframes. With this technique, mainframes can allocate their own resources of central processing units, memories and peripherals to each partition via special operating systems. In addition, such a system can also include several virtual systems, each of which can operate with its own operating system. Logical partinioning is implemented on the hardware layer and ensures, for example in the case of memories, that each partition is allocated a specific addressing range which does not overlap with those of the other partitions. In the initial phase of logical partitioning each partition had its own central processing unit( CPU), later with micro partitioning one central processing unit managed several LPARs.

As for the fineness of the partitioning, it is called granularity. Depending on the mainframe series, such systems can manage 60 or more logical partitions and patition the hardware resources.

The technique of partitioning was developed by IBM in the 1990s for its mainframes and later adopted in the other mainframe series, including those not designed as mainframe servers.