Specifications

Escala Tower PL & S, E, T System Hardware
Chapter 1: Family Overview 5/30
9es3s1c1.doc
Rev 5.9
02/12/2003
1.3. Logical Partitioning
Partitioning provides the ability to subdivide high-end systems into smaller partitions that are capable
of running a version of an operating system or a specific set of application workloads.
The main reasons for partitioning a large system are as follows:
•
Server consolidation by running multiple applications that previously resided on separate physical
systems.
•
Mixing production and test environments.
•
Consolidation of multiple versions of the same operating systems.
•
Consolidation of applications requiring different time zone settings.
•
Performing software upgrades while continuing to run applications in a separate partition.
•
Application isolation: running applications in separate partitions helps ensure they cannot interfere
with one another in the event of a software failure in one partition.
If high availability is critical, the implementation of high availability failover capability between
partitions in separate servers is recommended.
A logical partition consists of CPUs, memory, and I/O slots and their attached devices that are
typically a subset of a pool of available resources within a system. LPAR differs from Physical
Partitioning (PPAR) in the way resources are grouped to form a partition. Logical partitions do not
need to conform to the physical boundaries of the building blocks (collection of resources) used to
build the server. Instead of grouping by physical building blocks, LPAR adds more flexibility and
freedom to select components from the entire pool of available system resources. This allows better
granularity, which maximizes the resource usage on the system and minimizes unnecessary resource
reallocation.
LPAR works within a single memory coherence domain so it can be used within a simple SMP with no
special building block structure. All the operating system images run within the same memory map,
but are protected from each other by special address access control mechanisms in the hardware, and
special firmware added to support the operating system.
Each partition runs its own copy of the 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 provide strong isolation between resources. Many types of errors, even those within shared
resources, are isolated inside the partition where they occur.
AIX Workload Manager (WLM) is an integral part of the LPAR strategy for AIX and is included as
part of the base AIX operating system. It provides system administrators with greater control over how
CPU, physical memory, and I/O resources are allocated to processes and applications. Resources can
be managed within a partition just as they are in an unpartitioned server.