DRS migrating anti affinitized virtual machines to the same ESXi host

Products

• VMware vCenter Server

Issue/Introduction

• Virtual machines are part of a DRS anti affinity group
• When a ESXi host hosting a virtual machine part of DRS anti affinity group is put into maintenance mode, DRS may migrate the virtual machine to another ESXi host which already has another virtual machine of the same anti affinity group

Environment

VMware vCenter server 8.x

Cause

By design, DRS will attempt to migrate anti affinitized virtual machines to the same ESXi host if the existing virtual machine is marked for migration off the ESXi host.

Resolution

This DRS behavior may cause an issue if the ESXi host does not have enough resources to accommodate both the anti affinitized virtual machines.

To workaround this issue, reserve 100% cpu and memory to both anti affinitized virtual machines. This will prevent DRS from initiating the migration while the other VM is in the process of migrating