Gabrie1
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Commander

DRS 1:1 vCPU:Core not working as expected

Hi,

Running vCenter 6.7u3j and for our Citrix VMS we want to run a 1:1 vCPU:Core overcommit, therefore setting the DRS tot 1:1, fully automated and the aggressiveness to the default 3. All hosts have 56 logical processors, that is 28 cores and 2 CPUs.

When I now load my hosts with VMs and deliberately overload one of them with 2 vCPU's too many, DRS doesn't kick in to VMotion the VM. When I click RUN DRS I don't see any recommendations and if I leave it alone for more than 5min, there is no new recommendation either.

When I look at the DRS Balance, it says:
Target: less than or equal to 0.126
Current: 0.036

Even after setting the aggressiveness to 4, the cluster remains balanced enough to not force a VMotion and maintain the 1:1 vCPU:Core ratio.Target: less than or equal to 0.063
Current: 0.039

Adding another VM with 4 vCPU to the first host, gives me 28 physical cores and 34 vCPU assigned on that host. The DRS balance changes to:
Target: less than or equal to 0.063
Current: 0.047

It seems that even though 1:1 vCPU:Core is set, DRS still takes in account the CPU load for balancing the VMs. Is that correct?

I would have expected that even if the VMs were doing next to nothing in CPU and Memory load, DRS would try to maintain the 1:1 ratio. Is that an incorrect assumption?

http://www.GabesVirtualWorld.com
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