IBM – Live Partition Mobility for Oracle RAC

This paper documents the concept and recommendation of using Live Partition Mobility (LPM) in an Oracle RAC environment.
It describes the configuration of the IBM Power systems infrastructure and Oracle RAC to perform the Live Partition Mobility of an Oracle RAC node.
The paper describes two scenarios, the first is given as example for test purpose in order to setup the configuration and understand the interaction of all components.
The second scenario is the officially supported LPM process for an Oracle RAC environment.
This paper is illustrated with a real example of the LPM of a RAC node from a Porwer6 processor based source server to a Power7 target server.

Introduction

Live Partition Mobility (LPM) is a feature of PowerVM Enterprise Edition which allows for moving an LPAR from an IBM Power system to another physical IBM Power system.
LPM increases availability of the application and improves workload management. LPM improves flexibility of the entire infrastructure as you are able to continuous run the applications during planned maintenance of your server, by migrating without disruption the logical partitions to another server.
Also you are able to easily manage the applications workload by migrating LPARs and get free CPU and Memory resources for your most important workload production running on the source server.
Both source and target systems can be POWER6 or POWER7 processor based. The I/O adapters configured in the AIX LPAR must be defined as virtual devices and requires that the network and the SAN disk be accessed though a Virtual I/O Server Partition. LPM feature is not compatible with physical resources, so they have to be removed at least for the LPM operation, and if any, reattached to the LPAR after the migration.
Remember that you can keep physical adapters configured in the LPAR and also configure virtual adapters as a backup path for the network access and heterogeneous multi-path for the SAN disk access.
Also all the disks have to be defined from the SAN and shared to VIO servers of both source and target servers.
LPM process consist of several steps, such as reading the LPAR configuration on the source server to create it on the target server, creating the virtual devices at the target VIO Server, copying the physical memory blocks from the source to the target server, activating the LPAR on the target server and starting the AIX processes on the target server partition.
Once the processes are running on the target server partition, the virtual devices corresponding to the LPAR are removed from the source VIO Server and the LPAR is deleted on the source server.
The major migration step is the copy of the logical memory blocks (LMBs) though the network while AIX processes are running. At the end of the memory copy, almost 95%, a checkpoint operation is done and the processes are run from the target server. Depending on the amount of memory assigned to the LPAR and on the memory activity of the running processes, this checkpoint operation may freeze the processes for a short duration.

From an Oracle RAC environment point of view, this step is the most critical and requires some certification tests. That is the reason why as the time of writing, LPM is supported for Oracle single instance database and Oracle RAC is not officially supported.
In the following you will see a functional example of LPM operation in Oracle RAC environment, so you can run it as a test without support from both IBM and Oracle.
The supported process for LPM operation in an Oracle RAC environment consists in stopping Oracle for the migration step while keeping AIX alive.

Live Partition Mobility for Oracle RAC

LPM_a_RAC_node_July 27 2011
Enjoy…

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