vCenter Server indicates that the Distributed Resource Scheduler usage load is imbalanced

Products

• VMware vCenter Server

Issue/Introduction

• DRS usage load is not evenly balanced across hosts.
• Some hosts within a DRS Cluster show significantly higher CPU and/or memory usage compared to other hosts in the cluster.
• DRS resource distribution charts indicate that load is not distributed evenly across the hosts in the cluster.

Cause

The DRS process may decide not to initiate migrations of virtual machines to other hosts within the cluster if the cost involved outweighs the benefit obtained. Load balancing migrations have a cost but no additional benefit, if the required resources are available to virtual machines running on the host.

Resolution

The primary goal of the DRS is to provide virtual machines within a cluster with access to the required resource. DRS is not designed to evenly balance resource usage across hosts in the cluster.

High memory or CPU utilization of an individual host is not a sufficient reason to migrate virtual machines if the host is able to provide 100% of the resources required for its running virtual machines. This cluster imbalance can be safely ignored, if there is no observed performance degradation in virtual machines.

If a host within the DRS cluster is unable to provide a virtual machine with the resources it requires, then DRS migrates the virtual machine to a host that can provide the required resources.