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    Hyper V dynamic Memory Could cause Kernel Panic :Memory hot add failed

    Hyper V dynamic Memory Could cause Kernel Panic :Memory hot add failed

    I've been reported that One of Our RHEL 5.8 Server is getting panicked and continuously booting. This is the server which we have Migrated to Hyper V recently. I get into the Job and tried to scrutinize  the Console logs. Find out that the server is getting panicked while trying to Oracle related Services up.
     First thing i did was to disable the Oracle auto start and then start the server back.  

     When the server came back I found that server is running with 1GB of Memory. That forced me to think the memory mapping of the HyperV host. My instinct was right. It is a Box with Dynamic Memory allocated , in Microsoft Language Hv ballooning. Then I did run following command to Confirm. The hv_balloon parameter confirms that  Dynamic Memory is set.

    [root@Server1 ~]#  lsmod | grep hv
    hv_netvsc              62592  0
    hv_balloon             48023 0 [permanent]
    hv_utils               67128  1
    hv_storvsc             51348  2
    hv_vmbus               87056  4 hv_netvsc,hv_utils,hyperv_fb,hv_storvsc
    scsi_mod              199129  12 be2iscsi,ib_iser,iscsi_tcp,bnx2i,libcxgbi,libiscsi2,scsi_transport_iscsi2,scsi_dh,sg,libata,hv_storvsc,sd_mod
    [root@Server1 ~]#


    Then I go on start the Oracle Services,and found out that "hv_ballon" is unable to add dynamic memory.

    Server1 kernel: hv_balloon: Memory hot add failed
    Server1 kernel: hv_balloon: Received INFO_TYPE_MAX_PAGE_CNT
    Server1 kernel: hv_balloon: Data Size is 8

    Finally i shutdown the server and disable dynamic Memory. Then add static memory to the Virtual machine. Started the machine and confirmed that if the kernel cached that or not. yes it does.

     lsmod | grep hv

     [root@Server1 ~]#  lsmod | grep hv
    hv_netvsc              62592  0
    hv_utils               67128  1
    hv_storvsc             51348  2
    hv_vmbus               87056  4 hv_netvsc,hv_utils,hyperv_fb,hv_storvsc
    scsi_mod              199129  12 be2iscsi,ib_iser,iscsi_tcp,bnx2i,libcxgbi,libiscsi2,scsi_transport_iscsi2,scsi_dh,sg,libata,hv_storvsc,sd_mod
    [root@Server1 ~]#


    Then I Started the services on the Machine, Which is Happy to Do that.

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