vCenter

  • 1.  DRS moving only one VM

    Posted Mar 31, 2020 02:12 PM

    HI gays, I hope you all are healthy and well.

    Recently I notice one straight thing.

    I have custer with four host, and DRS set up to full automate and migration threshold on 3 . also Individual virtual machine automation levels enabled.

    There is more than 80 VMs. But one VM migrates between host a lot, more than 60 times over 24 hours.   Hosts are on 50% CPU and 60% od RAM.

    I can not find a reason why that particular VM is always migrated, also I am confused  why DRS is trigger when DRS conditions are not fulfilled.



  • 2.  RE: DRS moving only one VM
    Best Answer

    Posted Mar 31, 2020 03:24 PM

    Looks Like VM demand more resource that the reason VMs frequently moving around. Have you check the VM utilization ? If not please check is there any specific time moving the VM.

    DRS looks for the demand for every running VM in the cluster. VM demand is the amount of resources that the VM currently needs to run. For CPU, demand is calculated based on the amount of CPU the VM is currently consuming.

    DRS also collects resource availability data from each and every VM and host in the cluster. Data like VM CPU average and VM CPU max over the last collection interval depict the resource usage trend for a given VM, while availability data like VM CPU Ready Time2 and VM Memory Swapped3 indicate resource shortage, if any, for the VM (availability data indicate if a VM is running short of resources). DRS then correlates the resource usage data with the availability data and runs its load balancing algorithm before taking necessary vMotion actions in order to keep the cluster balanced and to ensure that VMs are always getting the resources they need to run.



  • 3.  RE: DRS moving only one VM

    Posted Apr 02, 2020 06:24 AM

    hi,

    VM is't the stronger VM in cluster , also there are several VM with more cpu and more RAM on wich usage  of CPU is constantly hight but DRS don't trigger for them.

    FOr this particular VM CPU ready is hight average 100ms , so that is the reason why DRS constantly migrate .



  • 4.  RE: DRS moving only one VM

    Posted Apr 01, 2020 04:02 PM

    Hi,

    Which version of vCenter/ESXi are you using ?

    Does the VM that keeps bouncing around is one of the biggest (CPU/RAM) you have in your cluster? is the CPU/RAM demands very high ?

    Another way to investigate and troubleshoot is to set DRS to "partially automated" while you are working in vCenter to catch the reason that triggers DRS and what improvement should result, and then manually validate the recommendation (switch it back to fully automated before leaving though)

    Indeed, level 3 DRS will apply recommendations that promise at least good improvement to the cluster’s load balance.

    Cedric