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VMware Round Robin Settings

  • 1.  VMware Round Robin Settings

    Posted Tue March 30, 2021 12:02 PM
    Hi all,

    We have a customer who has an SVC with backend IBM storage, who have defined multiple storage pools, some flash only, the rest being Easy Tier pools (with SAS HDD's), and soon to have some Flashcore/SCM also behind the SVC. In doing an online Flashsystem Tour guide, it mentions this VMWare recommendation for flash based systems to improve performance:

    VMware Knowledge Base

    My query is given the customer has a mix of HDD and SSD behind their SVC layer, and not 100% flash, should we still go ahead and get the hosting teams to change their ESXi settings as per above to realise the performance improvement?

    Thanks, Andy

    Andrew Hodgson

  • 2.  RE: VMware Round Robin Settings

    Posted Wed March 31, 2021 02:23 AM
    Yes, you should update this settings on all datastores. This setting utilizes your paths to your storage. If a datastore runs around 800 iops it's only uses one path due to this setting. If you have 4 paths update this setting to 1 each io request distributed to all active paths and utilizes all. 

    and its recommended to set the XCopy transfer size to 4096


  • 3.  RE: VMware Round Robin Settings

    Posted Wed March 31, 2021 08:26 AM
    Hi Andy. You may want to review the Knowledge Center that covers all our recommended VMware settings while you're at it! The  following is for the FS9200 but same recommendations for all systems running Spectrum Virtualize (i.e. not FS9200 specific)  . This is for hosts connected over FC but we have other links for hosts connected via iSCSI/iSER/NVMe as appropriate as you'll see.
    We're also in the midst of updating our Spectrum Virtualize and VMware Redbook as well.

    Brian Sherman
    Distinguished Engineer
    Markham ON

  • 4.  RE: VMware Round Robin Settings

    Posted Wed March 31, 2021 08:43 AM
    Thanks both for your responses.

    I'd found those sections in the IBM docs also you mention Brian just after I'd posted this thread, and have passed them on to our VMware support guys. They are very receptive to the changes being suggested and we are planning to apply them to our dev environment soon and assuming it goes well, do the same to our prod environment also. 

    I'll report back as and when we get these VMware changes applied.

    Andrew Hodgson

  • 5.  RE: VMware Round Robin Settings

    Posted 20 days ago

    Hi Andrew,

    Would you be so kind to share your expriences and findings?


    Istvan Buda