Capabilities

When you configure an LPAR on the HMC (outside of HACMP), you provide LPAR minimum, desired, and maximum values for the number of CPUs and amount of memory. These values can be obtained by running the lshwres command on the HMC. The stated minimum values of the resources must be available when an LPAR node starts. If more resources are available in the free pool on the frame, an LPAR can allocate up to the stated desired values.

During dynamic allocation operations, the system does not allow that the values for CPU and memory go below the minimum or above the maximum amounts specified for the LPAR.

HACMP obtains the LPAR minimums and LPAR maximums amounts and uses them to allocate and release CPU and memory when appservers are started and stopped on the LPAR node.

HACMP requests the DLPAR resource allocation on the HMC before the appservers are started, and releases the resources after the appservers are stopped. The Cluster Manager waits for the completion of these events before continuing the event processing in the cluster.

HACMP handles the resource allocation and release for appservers serially, regardless of whether the resource groups are processed in parallel. This minimizes conflicts between appservers trying to allocate or release the same CPU or memory resources. Therefore, carefully configure the cluster to properly handle all CPU and memory requests on an LPAR.

These considerations are important:

After HACMP has acquired additional resources for the appserver, when the appserver moves again to another node, HACMP releases only those resources that are no longer necessary to support this application on the node.

HACMP does not start and stop LPAR nodes.

It is possible to create a custom event or customize application start and stop scripts to stop LPAR nodes if desired.

The granularity of what HACMP can manage is the physical CPU for dedicated processors, and virtual processors for shared processors configuration. With micropartitioning, HACMP works with virtual processors, and not physical processors. In a mixed environment, HACMP does the verification of the possibility to add the resources to respect the maximum value.

For dedicated processor mode, the maximum value unit is the physical processor. For shared processor mode, the maximum value unit is the virtual processor. The free pool resources is calculated by adding the desired capacity entitlement (CE) values of each partition in shared processor mode, and the physical processor in dedicated processor mode.