HP Instant Capacity (iCAP) manual Deactivating Cores in nPartitions, Partition Constraints

Deactivating Cores

You can decrease processing capacity instantly on HP enterprise servers with the Instant Capacity software (even on servers with sufficient usage rights for all cores to be active simultaneously). Any number of active cores can be deactivated at any time, within the following partition constraints. Core deactivation can be useful for load balancing cores in nPartitions (hard partitions) of Instant Capacity systems.

Deactivating Cores in nPartitions

The software provides two types of core deactivation:

•Instant (icapmodify command’s default behavior) — deactivation occurs immediately.

•Deferred (icapmodify -D) — deactivation occurs after the next reboot of the partition.

Instant deactivation of cores occurs when the icapmodify command is used with the -doption but without the -Doption.

IMPORTANT: On OpenVMS Instant Capacity systems, HP strongly recommends that you deactivate cores using the icapmodify or the ICAP SET command. The use of the STOP CPU command on an Instant Capacity system can result in unintended consequences, such as a reactivation of the core when an Instant Capacity reconciliation transaction is requested.

Deferred deactivation of cores occurs when the icapmodify command is used with both the -Dand -doptions. With the deferred option (-D), core deactivation occurs after a reboot of the partition. The scheduled timing of the reboot (and the core deactivation) can take place at a planned time. For example, if you deactivate cores in deferred activation mode and schedule a partition reboot to occur on the first day of the next month, the cores are deactivated at that time.

Since deferred deactivation does not immediately decrease the number of active cores, compliance checking is not affected by deferred deactivation.

To deactivate one or more active cores, use theicapmodify command as root. For details, see icapmodify(1M).

Partition Constraints

An nPartition must have a minimum of one active core for each active cell. Deactivation of cores is limited by this rule. If the deactivation applies to a virtual partition, additional constraints might apply, such as the minimum number of cores specified for the virtual partition.

Example Deactivation Session for Hardware-Partitionable Systems

Example 4-4 (page 60) shows how to deactivate an active core. At the beginning of this deactivation session, there are a total of 4 cores in the partition; 3 cores are active and 1 is inactive. In this example, 1 active core is deactivated, leaving the partition with 2 active cores and 2 inactive cores. As with activation, you do not specify a particular core to be deactivated. You specify only the number of cores to be deactivated.

Deactivating Cores 59