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Why is the default size for the FailoverClustering_Diagnostic log 18014398507384832 KB?

Brian Illner 31 Reputation points
2020-11-06T14:26:43.697+00:00

We have two Server 2019 Hyper-V Clusters currently running in our environment. After researching some unexpected C drive freespace loss, we discovered that the FailoverClustering_Diagnostic log size on each host in both clusters was set to 18014398507384832 KB (or 18014 PB).

We certainly didn't manually set these to such an absurd size, so was this the default? Or did something else change it?

Hyper-V
Hyper-V
A Windows technology providing a hypervisor-based virtualization solution enabling customers to consolidate workloads onto a single server.
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Windows Server Clustering
Windows Server Clustering
Windows Server: A family of Microsoft server operating systems that support enterprise-level management, data storage, applications, and communications.Clustering: The grouping of multiple servers in a way that allows them to appear to be a single unit to client computers on a network. Clustering is a means of increasing network capacity, providing live backup in case one of the servers fails, and improving data security.
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  1. Xiaowei He 9,906 Reputation points
    2020-11-11T03:13:28.613+00:00

    Hi,

    I tested in my lab and get the same result with you on the Server 2019 cluster (Clean install of Server 2019 OS not upgrade):

    38905-microsoftteams-image-5.png

    In this situation, I would suggest you turn to uservoice to feedback this issue:

    https://windowsserver.uservoice.com/forums/295047-general-feedback

    Thanks for your time!
    Best Regards,
    Anne

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  1. David Marcus 1 Reputation point
    2022-06-17T14:55:17.117+00:00

    We just found out about this issue the hard way.

    We have two long-standing Windows Server 2019 Hyper-V clusters, and all hosts have the FailoverClustering_Diagnostic max log size set to 18014398507384832 KB (18 petabytes).

    Went to install updates on one of the hosts and found the c: drive was full. The FailoverClustering_Diagnostic log was 102 GB with 180 million events dating back to 2019.

    I've confirmed that all seven hosts (a 4-node cluster and a 3-node cluster) are set the same.

    Will manually changing the max size permanently correct this, or will they still revert to the bad value?

  2. Brian Illner 31 Reputation points
    2022-06-17T15:37:10.697+00:00

    @Xiaowei He

    I reported this 7 months ago on the Feedback hub after Microsoft retired the UserVoice platform.

    https://aka.ms/AAh98rf

    No idea why it is not receiving any traction or escalation, especially since you yourself confirmed that it is a bug.

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