CSVBalancer Windows Server 2019 with S2D enabled

Jim Gandy 121 Reputation points
2021-01-13T01:52:27.09+00:00

Does csvbalancer work on Azure Stack HCI/Server 2019 S2D? Been testing it in our LAB and it does not seem to move the VMs to the owner of the CSV the VHDX files reside as it has in older Server versions.

Azure Stack HCI
Azure Stack HCI
A hyperconverged infrastructure operating system delivered as an Azure service that provides security, performance, and feature updates.
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  1. Steven Ekren 166 Reputation points
    2021-01-13T18:04:41.403+00:00

    @Jim Gandy
    No, its turned off because every time you move a CSV, everything in the CSV cache gets reset and has to be rebuilt as reads come in on the new node. We found that it's actually better to have a slight imbalance then to balance it as far as perf impact.

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  1. Brian Murphy 21 Reputation points
    2021-01-13T23:18:30.287+00:00

    @Steven Ekren
    I'm confused about this. You said it's turned off and that's true by default, but the feature still exists (i.e. I can still set "(get.cluster).csvbalancer = 1") and I can't find any documentation from MS saying it no longer does anything if you enable it. However, it doesn't seem to work for me either in 2019 (did on my 2016 S2D cluster). Which is unfortunate, because I see a huge an immediate performance benefit on one of my specific VMs if it runs on the host that owns the disk that the VHDX files reside on. Which is what CSV balancer did for me automatically.

    So is it actually no longer supported and no expected to work even if you enable it?

    If so I might look at scripting a scheduled task to do the same thing. I don't find that I'm moving CSVs or VMs around between my hosts very often (maybe once a month when I do updates), so the impact of rebuilding the cache doesn't seem prohibitive to me.

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  2. Darryl van der Peijl 76 Reputation points
    2021-01-14T07:33:17.98+00:00

    Hi @Brian Murphy ,

    These are two separate things.

    • CSV Balancer, handles the distribution of Cluster Shared Volumes
    • AutoBalancerMode, handles the distribution of VMs, see blog here.

    To my knowledge, VMs will move to a host in the fault domain where the storage resides.
    Based on the setting described in the blog, it will do so on a node join or at a timed interval.

    Regards,

    Darryl van der Peijl
    Splitbrain

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