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  • 1.  New Blog: Introduction to SR-IOV and vNIC for IBM i

    Posted Mon November 14, 2022 08:58 PM
    I've decided to start posting a few articles regarding virtualization topics specifically for IBM i Administrators and decision makers.

    My first article is an introduction to SR-IOV and vNIC with some pointers to where you can get the full details.

    Introduction to SR-IOV and vNIC for IBM i

    I welcome comments about the article and suggestions for future topics.

    Thanks for checking it out.

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    Introduction to SR-IOV and vNIC for IBM i
    This is the first in a series of articles on frequently overlooked Power systems features that highlight the value for IBM i customers, starting with sharing Ethernet adapters with SR-IOV, and the added benefits that can be achieved with vNIC technology on top of SR-IOV.
    View this on Vios4i >


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    Vincent Greene
    IT Consultant
    Technology Services
    IBM
    Vincent.Greene@ibm.com


    The postings on this site are my own and don't necessarily represent IBM's positions, strategies or opinions.
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  • 2.  RE: New Blog: Introduction to SR-IOV and vNIC for IBM i

    Posted Tue November 15, 2022 03:18 PM
    Hi Vincent,

    Very helpful article, thanks. I've recently configured  vNIC failover for IBMi and I was wondering if you have any recommendation on the number of backing devices per active VF. I see maximum is 8, but does that make any sense or just two is enough and are there any implications if you use high number of backing devices?

    Do you have any recommendations in terms of performance settings for example MTU size on IBMi side etc?

    Regards,
    Tsvetan

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    Tsvetan Marinov
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    Original Message


  • 3.  RE: New Blog: Introduction to SR-IOV and vNIC for IBM i

    Posted Tue November 15, 2022 08:36 PM
    Hi Tsvetan,

    Thanks for checking it out, glad you found it helpful.

    I always aim for a minimum of two backing devices through separate VIOS and redundant ethernet switches whenever possible.  I try to balance the priorities so there are roughly the same number of active interfaces per VIOS/Ethernet switch in normal operation.

    I have configured up to four in cases where we were using four VIOS, but so far I've never configured more than four.

    I think the key factor in deciding is where you can get more redundancy in your system configuration.  If your system has enough independent buses to benefit from more than the minimum two, you can gain redundancy from bus level hardware failures by putting adapters on different buses and using more VIOS, or maybe just more vNIC backing devices with two VIOS.

    The key factor is redundancy.  Two backing devices on a different ports on single card to different switches protects from switch, cable, and port failures, but not adapter or bus failures.  If you move that to separate adapters in different racks, you've got more redundancy.  You can get more protection on an enterprise E1080 than on the smaller scale out servers.

    From a resource perspective, each backing device uses Hypervisor and VIOS memory, so more backing devices means more memory.  Whatever you do, don't skimp on memory for your VIOS if you want your vNIC failover to work.

    If your network supports it end to end (many don't), using jumbo frames can have a significant impact on your performance.  The key part here is to set your physical MTU to no more than what your network infrastructure can handle.  A low MTU (~1500) on the physical port on a network that support jumbo frames is leaving some performance on the table, but a jumbo frame MTU (~9000) on that same physical port when the switches don't support it will absolutely DESTROY your performance.   Definitely talk with your network team before making any changes, and do your research.  Each environment is unique.






    ------------------------------
    Vincent Greene
    IT Consultant
    Technology Services
    IBM
    Vincent.Greene@ibm.com


    The postings on this site are my own and don't necessarily represent IBM's positions, strategies or opinions.
    ------------------------------

    Original Message