Configure memory QoS

About memory QoS

Memory QoS increases VM density to reduce costs by allowing for memory overcommitment. The system by default assigns 4 GB of memory to each VM upon VM creation. A host dynamically adjusts the memory of each VM on the host based on workloads of VMs.

Memory quota

The memory quota is the size of memory assigned to a VM. You can adjust the memory quota as needed. The maximum memory quota is 16 times the memory size assigned to a VM in VM creation or the memory size of the host where the VM resides, whichever is larger.

The maximum memory quota displayed for a shutdown VM is the memory size of the host where the VM resides.

 

Memory reservation

The reserved memory is the minimum amount of memory that a VM can obtain. Reserve memory to ensure correct operation of a VM when memory resources are insufficient. The VM is assigned the reserved memory exclusively. Other VMs on the same host cannot preempt that part of memory even if the VM uses less memory than reserved.

If you set the reserved memory percentage to 0%, no memory is reserved for a VM. If you set that parameter to 100%, a VM obtains all memory of the host where it resides.

Memory resource priority

A memory resource priority determines the sequence in which VMs are assigned memory resources when the VMs are competing for memory resources. When memory resources are insufficient, the VMs with high memory resource priority take precedence. If you do not reserve memory resources for a VM, the system assigns memory resources to the VM based on its memory resource priority.

Memory resource priorities can be high, medium, or low. The system allocates memory resources to VMs with high, medium, and low memory resource priorities in a ratio of 4:2:1.

 

A memory resource priority takes effect only when VMs are competing for memory resources. If memory resources are sufficient, a VM can obtain as much memory as requested.

 

Procedure

1. On the top navigation bar, click Resources.

2. From the left navigation pane, select Host Pool Name > Cluster Name > Host Name > VM Name or Host Pool Name > Host Name > VM Name.

3. Click Edit.

4. Click the Memory tab.

5. Configure the following settings:

• Quota: Edit the memory size to be assigned to the VM.

• Reserve: Enter the memory to be reserved for the VM to the total available memory of the host in percentage.

• Limit: Enter the maximum memory size that the VM can use.

• Resource Priority: Select the priority for the VM to request memory resources.

Figure-1 Editing memory settings