PowerVM

  • 1.  Memory Virtualization

    Posted Thu April 29, 2021 09:30 PM
    Hi,

    Has anyone implemented the PowerVM Memory Virtualization capabilities all together (Active Memory Sharing + Active Memory Deduplication + Active Memory Expansion)? I would like to know what was the type of workloads running on the selected LPARs, what was the observed gain and complexity related to managing the environment after implementation.

    So far, I only used Active Memory Expansion for AIX LPARs running SAP Systems with expansion factors between 1.4 and 2.0 and I was able to see interesting gains with very low cpu consumption.

    Reference material: IBM PowerVM Virtualization Introduction and Configuration SG247940 and IBM PowerVM Virtualization Managing and Monitoring SG247590.

    Regards,
    Felipe Bessa


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    Felipe Bessa
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  • 2.  RE: Memory Virtualization

    Posted Fri April 30, 2021 07:07 AM
    AME (Active Memory Expansion) is being used by many customers to logically increase the amount of memory available in a VM.

    AMS (Active Memory Sharing) and its corresponding feature Active Memory De-duplication are not used much on PowerVM.  When the memory is over-committed the PowerVM Hypervisor needs to page memory from disk though the VIOS.  I believe these performance issues have impacted the adoption.   If you would like more information about AMS, feel free to contact me heyrman@us.ibm.com.

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    Pete Heyrman
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  • 3.  RE: Memory Virtualization

    Posted Fri April 30, 2021 08:08 AM
    Hi Felipe:

    Couple of years  back I had attempted Live Partition  Mobility (LPM) with Active Memory Sharing (AMS) on a 8286-42A (that system is still with me) and it did not go too well. At that time I was told that LPM was not supported with AMS on POWER8. Since then, there have been significant changes to the Firmware and I am not sure if we have regressioned that feature and started to support.  Probably it might be fully supported  with POWER9. This is something I wanted to bring to your attention.

    Good luck with your implementation and  please share your experience.

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    Sridhar Murthy
    Senior Certified IT Specialist
    IBM
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  • 4.  RE: Memory Virtualization

    Posted Fri April 30, 2021 02:34 PM
    Hi Sridhar,

    Thank you for your comments and advice.

    According to the POWER9 9040-MR9 and POWER8 9119-MME servers manual, Live Partition Mobility (LPM) for LPARs using Active Memory Sharing (AMS) is fully supported. But some points must be noted.

    https://www.ibm.com/docs/en/power9/9040-MR9?topic=mobility-configuration-validation-partition
    https://www.ibm.com/docs/en/power8/9119-MME?topic=mobility-configuration-validation-partition


    For a mobile partition that uses shared memory, checks the following configuration:
    • The number of active VIOS partitions (subsequently referred to as paging VIOS partitions) that are assigned to the shared memory pool on the destination server.
    • That an available paging space device exists on the destination server and that the device satisfies the following requirements:
      • It satisfies the redundancy preferences that you specify.
      • It meets the size requirements of the mobile partition (it is at least the size of the maximum logical memory of the mobile partition).

    For example, you specify that the mobile partition uses redundant paging VIOS partitions on the destination server. You can migrate the mobile partition if the destination server provides the following configuration:

    • Two paging VIOS partitions are assigned to the shared memory pool.
    • An available paging space device exists.
    • The paging space device meets the size requirements of the mobile partition.
    • Both paging VIOS partitions on the destination server have access to the paging space device.

    Regards



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    Felipe Bessa
    Independent IT Consultant
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  • 5.  RE: Memory Virtualization

    Posted Fri April 30, 2021 03:05 PM
    Hi Pete,

    Thank you for your comments.

    I totally agree that physical overcommit might impact performance and should be avoided.

    According to the manuals I mentioned, I think that it would be valid to use these capabilities all together for workloads that meet specific characteristics in a logical overcommit scenario (SG247940 pg.149).

    However, I am concerned about the effort required to monitor the performance of the environment after this setup and react in case of overall poor performance. This is the reason why I would like to know if there are any documented use cases or experiences that could be shared.

    Regards


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    Felipe Bessa
    Independent IT Consultant
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