Overview of DLPAR and CoD

The applications running on LPARs are completely isolated from each other at the software level. Each LPAR can be optimally tuned for a particular application that runs on it.

In addition, Dynamic Logical Partitioning (DLPAR) allows you to dynamically allocate additional resources (such as memory and CPUs) to each logical partition, if needed, without stopping the application. These additional resources must be physically present on the frame that uses logical partitions.

PowerHA® SystemMirror® can dynamically use the Capacity on Demand (CoD) resources (On/Off CoD resources or Enterprise Pool CoD resources) and activate or allocate these resources. This process allows the frame to receive more configurable resources that can be allocated to the LPAR through DLPAR operations. The Resource Optimized High Availability (ROHA) function in PowerHA SystemMirror manages DLPAR and CoD operations.

LPAR, DLPAR, and CoD terminology

Logical Partition (LPAR)

The division of a computer's processors, memory, and hardware resources into multiple environments so that each environment can be operated independently with its own operating system and applications.

The number of logical partitions that can be created depends on the system. Typically, partitions are used for different purposes, such as database operation, client/server operations, web server operations, test environments, and production environments. Each partition can communicate with the other partitions as if each partition is a separate machine.

Dynamic Logical Partitioning (DLPAR)

A facility in some IBM Power Systems processors that provide the ability to logically attach and detach a managed system's resources to and from a logical partition's operating system without rebooting the system. The following features are available in a DLPAR:

Capacity on Demand (CoD)

A feature of IBM Power Systems servers that you can use to activate preinstalled but inactive processors when resource requirements change.

Dynamic Processor Deallocation

A feature of IBM Power Systems servers and some SMP models. The processor is taken offline dynamically when an internal threshold of recoverable errors is exceeded. DLPAR allows substitution of the inactive processor, for the processor that is suspected of being defective. This online switch does not affect applications and kernel extensions. This function is not supported by PowerHA SystemMirror.

Cross-partition workload management

A feature that is used to manage system resources across partitions. This function is not supported by PowerHA SystemMirror.

Capacity on Demand (CoD)

A function in some IBM Power Systems processors you can use to acquire, but not pay for a fully configured system. The additional CPUs and memory, while physically present, are not used until you decide that the additional capacity you need is worth the cost. This provides you with a fast and easy upgrade in capacity to meet peak or unexpected loads. CoD is composed of the following resources:

Note: The following resources are managed through the ROHA function in PowerHA SystemMirror.

On/Off CoD

Resources that are preinstalled in your system, but you have not paid for the resources or activated the resources. You can use this type of CoD license to temporarily activate resources.

Trial CoD

Resources that are available to be used for a limited number of days. You do not have to pay for this type of CoD license.

Enterprise Pool CoD (EPCoD)

Resources that can move between systems in the same EPCoD pool to where the resources are needed. Physical resources such as CPU and memory are not moved between systems, but rights to access the physical resources are moved between systems. The rights to use resources are shared across systems. You can allocate the resources where they are required.

Hardware Management Console (HMC)

An interface that you can use to collect CoD system profile information and enter activation codes for CoD. You must manually enter the activation codes for CoD in the HMC.

The HMC also manages all DLPAR, On/Off CoD, Trial CoD, and EPCoD operations for the LPARs created on the CEC frame. PowerHA SystemMirror automatically performs all DLPAR, On/Off CoD, Trial CoD, and EPCoD operations for starting, stopping, and moving resource groups.

For integration with PowerHA SystemMirror, HMC must have a TCP/IP connection to the LPAR and a configured IP label through which a connection is established. Also, the Secure Shell (SSH) link must be established between all LPARs and the HMC. The lshmc command displays the HMC configuration.

ROHA function uses the AIX® ping command to verify connectivity with HMC.

Managed System

Am IBM Power Systems that is LPAR-capable and that is managed by an HMC.

CoD Vital Product Data (VPD)

A collection of system profile information that describes the hardware configuration and identification numbers. In this document, VPD refers to CoD VPD.

Activation Code (or License Key)

A password that is used to activate a processor that is inactive (standby) or to activate memory in CoD. Each activation code is uniquely created for a system and requires the system Vital Product Data (VPD) to ensure correctness.

Note: In the PowerHA SystemMirror SMIT interface and in the PowerHA SystemMirror documentation, the activation code is also referred to as the license key.