Saturday, 20 February 2016

VMware Virtual Machine's resources allocation common Best Practices !

While allocating RAM or CPU to a Virtual Machine In VMware, we always thinks that how much memory or CPU should we allocate to a Virtual machine.

The answer is, Allocate minimum as much as you can according your application requirement running on the Virtual Machine. Because, over allocating resources to a virtual machine slow down the performance instead of improving it.

Do not over allocate Resources (CPU/RAM) )to a Virtual Machine. Provide only required resources to a VM. Start by giving minimum number of vCPUs to the VM and keep on increasing them gradually until the VM perform as intended.

Example: I am taking an Example of a Virtual Machine with over allocated CPU cores.
Sometime you can observe that your ESXi host is hosting only one VM but the CPU usage of the Host is reaching to 100%. It happens, when a VM is oversubscribed in terms of CPU.

Another symptom is, if you will run ESXTOP command on the particular ESXi host, the affected VM’s Ready Percentage would be going up to 1000 or more which should be below 5.5 approx..

To check the ready percentage on ESXi host, SSH your ESXi host with root credentials > Run ESXTOP command and see the value highlighted in below screenshot:

If it is too high, please consider decreasing the CPU capacity and then monitor the performance of the VM. For more insight on this, you can refer the VMware KB:

To know more about Ready Percentage, see my another article:
What is Ready Percentage? 


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