VM Anti-Affinity Rules Not Enforced When DRS Is Disabled

Products

• VMware vCenter Server

Issue/Introduction

In a vSphere cluster a set of virtual machines (VMs) fail to separate across different hosts despite having anti-affinity rules configured and multiple VMs that should be distributed are residing on a single ESXi host.

The following messages can be observed within the vSphere client:

• Under the vSphere DRS Faults section, the message "Could not fix anti-affinity rule violation" is displayed.
• The DRS Faults Details section states "The virtual machine is pinned on the host".

Environment

vCenter 8.x 

Cause

The anti-affinity rule is not being enforced because Distributed Resource Scheduler (DRS) is disabled for the host where the affected virtual machines are running. Since anti-affinity rule enforcement relies on DRS automation, the virtual machines become "pinned" to the host. This prevents vSphere from performing the necessary vMotion operations to separate the VMs and satisfy the rule requirements.

Resolution

To resolve this issue, perform one of the following actions:

1. Re-enable DRS on the affected host.

2. Manually migrate the affected virtual machines to different ESXi hosts using vMotion to resolve the immediate rule violation.