Examples: Using processor compatibility modes in partition mobility

Moving an active logical partition from a POWER6 processor-based server to a POWER7 processor-based server

You want to move an active logical partition from a POWER6® processor-based server to a POWER7® processor-based server so that the logical partition can take advantage of the additional capabilities available with the POWER7 processor.

To accomplish this task, perform the following steps:

1. Set the preferred processor compatibility mode to the default mode. When you activate the logical partition on the POWER6 processor-based server, it runs in the POWER6 mode.
2. Move the logical partition to the POWER7 processor-based server. Both the current and preferred modes remain unchanged for the logical partition until you restart the logical partition.
3. Restart the logical partition on the POWER7 processor-based server. The hypervisor evaluates the configuration. Because the preferred mode is set to default and the logical partition now runs on a POWER7 processor-based server, the highest mode available is the POWER7 mode. The hypervisor determines that the most fully featured mode supported by the operating environment installed in the logical partition is the POWER7 mode and changes the current mode of the logical partition to the POWER7 mode.

At this point, the current processor compatibility mode of the logical partition is the POWER7 mode and the logical partition runs on the POWER7 processor-based server.

Moving the active logical partition back to the POWER6 processor-based server

A problem arises and you need to move the active logical partition back to the POWER6 processor-based server. Because the logical partition now runs in the POWER7 mode and the POWER7 mode is not supported on the POWER6 processor-based server, you need to adjust the preferred mode for the logical partition so that the hypervisor can reset the current mode to a mode that is supported by the POWER6 processor-based server.

To move the logical partition back to the POWER6 processor-based server, perform the following steps:

1. Change the preferred mode from the default mode to the POWER6 mode.
2. Restart the logical partition on the POWER7 processor-based server. The hypervisor evaluates the configuration. Because the preferred mode is set to POWER6, the hypervisor does not set the current mode to a higher mode than POWER6. Remember, the hypervisor first determines whether it can set the current mode to the preferred mode. If not, it determines whether it can set the current mode to the next highest mode, and so on. In this case, the operating environment supports the POWER6 mode, so the hypervisor sets the current mode to the POWER6 mode.
3. Now that the logical partition runs in the POWER6 mode and the POWER6 mode is supported on the POWER6 processor-based server, move the logical partition back to the POWER6 processor-based server.

Moving an active logical partition between different processor types without making configuration changes

Depending on how often you need to move logical partitions, you might want to maintain the flexibility to move an active logical partition between a POWER6 processor-based server and a POWER7 processor-based server so that you can move the logical partition back and forth without making configuration changes. The easiest way to maintain this type of flexibility is to determine the processor compatibility mode supported on both the source and destination servers and set the preferred processor compatibility mode of the logical partition to the highest mode supported by both servers.

To accomplish this flexibility, perform the following steps:

1. Set the preferred processor compatibility mode to the POWER6 mode because the POWER6 mode is the highest mode supported by both POWER6 processor-based servers and POWER7 processor-based servers.
2. Move the logical partition from the POWER6 processor-based server to the POWER7 processor-based server.
3. Restart the logical partition on the POWER7 processor-based server. The hypervisor evaluates the configuration. Remember, the hypervisor does not set the current mode higher than the preferred mode. First, the hypervisor determines whether it can set the current mode to the preferred mode. If not, it then determines whether it can set the current mode to the next highest mode, and so on. In this case, the operating environment supports the POWER6 mode, so the hypervisor sets the current mode to the POWER6 mode.
4. Do not make any configuration changes to move the logical partition back to the POWER6 processor-based server because the POWER6 mode is supported on the POWER6 processor-based server.
5. Move the logical partition back to the POWER6 processor-based server.
6. Restart the logical partition on the POWER6 processor-based server. The hypervisor evaluates the configuration. The hypervisor determines that the operating environment supports the preferred mode of POWER6, and sets the current mode to the POWER6 mode.

Moving an inactive logical partition between servers with different processor types

The same logic from the previous examples applies to inactive partition mobility, except inactive partition mobility does not need the current processor compatibility mode of the logical partition because the logical partition is inactive. After you move an inactive logical partition to the destination server and activate that logical partition on the destination server, the hypervisor evaluates the configuration and sets the current mode for the logical partition just like it does when you restart a logical partition after active partition mobility. The hypervisor attempts to set the current mode to the preferred mode. If it cannot, it checks the next highest mode, and so on.