Explanation of "CPU/Mem provisioned congestion" recommendations

Document created by dominic.grigg Expert on Aug 21, 2018Last modified by dominic.grigg Expert on Nov 14, 2018
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If you see host provision recommendations but the risk is "Memory Provisioned" or "CPU Provisioned" then this is actually something different than just host CPU / Mem utilisation congestion.

 

This is the virtual to physical ratio of CPU or memory. By default we set this capacity to as a 10 to 1 ratio (1000%)

 

Memory utilization may be low, but the risk of over-committing could still be very high depending on the size and amount of VMs in this cluster. Keep in mind if the recommendation is to provision a host the underlying causes can be a combination of many factors including high utilisation not just the one resource that's mentioned in the Risk description. Below is an example of a CPU provisioned congestion recommendation: 

 

 

By default the Mem/CPU overprovisioned host policy parameters are set to 1000 (%), a 10 to 1 virtual to physical ratio. This means that overprovisioning memory by 5 times the physical capacity shows up as 50% utilisation of the Mem Overprovisioned capacity in Turbonomic 


A provision recommendation will occur due, for example, to the ratio of vCPUs to physical CPUs going beyond the ratio of 10 to 1 or 1000% as shown in the screenshot  below. [edit suggestion: the recommendation will show not at peak value of 10x but at a value closer to Desired State (DS). So if DS is 70 and with diameter of 10 then the recommendation for action can occur at 6.5x. In other words, consider including the DS consideration in the statement.]

 

 

As mentioned, this is shown as 1000% in the host policy utilisation constraint option. This value can be increased to avoid this congestion recommendation .The current value represents a ratio of 10 vCPU to 1 CPU and 10 vMem capacity to 1 Mem capacity.

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