DRS does not load balance VMs evenly across the cluster.
Article ID: 403438
Updated On:
Products
VMware vSphere ESXi
Issue/Introduction
- DRS does not load balance VMs evenly across the cluster. While reviewing host metrics on the UI will observe that some hosts show higher memory utilization while others show very low memory utilization.
- This behavior is specifically observed where a large number of VMs have 3D graphics enabled, generally deployed using a template.
- A key symptom is a discrepancy between memory metrics displayed in the UI (showing "consumed" memory) and the data used by DRS (which includes "demand" and "reservations").
- Setting Migration threshold on cluster to max also doesn't migrate the VMs
Environment
vSphere 7.x
vSphere 8.x
Cause
The high memory demand observed by DRS is primarily attributed to a large number of Virtual Machines (VMs) configured with 3D graphics. Enabling this feature automatically sets a significant memory reservation (demand) within the VM. This reservation is factored into DRS's balancing calculations even when the memory is not actively used or consumed by the guest operating system. Consequently, DRS perceives higher host memory utilization than actual consumption, which leads to apparent uneven load distribution and discrepancies observed in host memory consumption metrics displayed in the UI.
Resolution
To resolve this issue, it is advisable to disable 3D graphics if they are not being utilized.
Additional Information
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