Dynamically modifying system resources using LKU with HMC profile
Overview
POWER systems currently provides DLPAR feature in order to modify the CPU, Memory etc values of an LPAR within the min and max limits, on a running LPAR. So, AIX users can use DLPAR operation (using drmgr command or from HMC GUI) to adjust the same. But using the DLPAR operations user is not allowed to adjust the resources beyond the max limits. In such a scenario user needs to shut down the LPAR and adjust min/max limits from HMC GUI, and then boot the LPAR. This approach results in the down time of the LPAR and also downtime of the running workload. To address this issues, LKU has introduced a new feature, using which user can adjust min/max resources on a running LPAR. With the new feature LKU provides a new tunable (clone_from_hmc_profile), using which user can increase the system resources without a need for LPAR reboot. This can be done by modifying the required values (min/max for CPU memory etc) in HMC profile and then attempting an LKU(with new tunable) after that. This feature is available from AIX 73 TL3 onwards.
Pre-requisites
Below URL has the prerequisites required for HMC based LKU.
https://www.ibm.com/docs/en/aix/7.3?topic=planning-prerequisites#lvupdate_requisite__title__2
The LPAR requirements for performing Live Update operations are listed in the URL below:
https://www.ibm.com/docs/en/aix/7.3?topic=planning-lpar-requirements
Live Update restrictions
The detailed list of Live Update restrictions is documented at the following URL:
https://www.ibm.com/docs/en/aix/7.3?topic=planning-restrictions
Detailed steps to use this feature
1) User should turnoff profile sync to use this feature. In other words one should set the option “Save configuration changes to profile” to “Disabled” so that they can edit the profile. The images used in this document are from HMC Version 10. This could change based on HMC version.
This option can be found at the “Partition properties” page in “General” section, under “Advanced Settings”.
2) Select the “Partition name” and select “Manage profiles” option under “Profiles” tab. Highlighted as below in red box for reference
3) Click on the “Partition profile name” that is “Last activated” profile.
4) Change the profile attributes in “Processors” and “Memory” sections as needed.
5) After editing the values in “Last activated” profile, save it.
6) Set clone_from_hmc_profile attribute to yes in lvupdate.data file under hmc section and attempt LKU to create the surrogate LPAR with modified system resource values. You can verify using “lparstat -i” command to see the values before and after LKU .
Apart from below list of attributes, user is not allowed to modify any other parameters in the HMC profile.
Memory related
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Minimum memory
Maximum memory
Below are applicable for Dedicated processor configuration.
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Minimum dedicated processors
Maximum dedicated processors
Below are applicable for Shared processor configuration.
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Minimum shared processing units
Maximum shared processing units
Minimum virtual processors
Maximum virtual processors
6) After completion of LKU, remove clone_from_hmc_profile attribute from lvupdate.data file under hmc section to avoid this feature for future LKUs.
About the authors
Sai Krishna Juturi (E-Mail : sai.krishna.juturi@ibm.com) - AIX Live Update Development
Vinod Kumar Boddukuri (E-Mail : vinod.boddukuri@in.ibm.com) - AIX Live Update Architect