Using Affinity Rules without vSphere DRS

Products

• VMware vSphere ESXi
• VMware vCenter Server

Issue/Introduction

You can use affinity rules without using vSphere DRS.

But it is not obvious what impact will have against various event or operation. (VM Power On, vMotion, vSphere HA failover)

Environment

VMware vSphere ESXi

VMware vSphere vCenter

Resolution

Following table shows each operation/event and ability to violate each rule.

	VM Power On	vMotion	vSphere HA Failover
VM-VM Affinity/anti-Affinity Rule	cannot violate (1)	can violate	cannot violate (2)
VM-Host Hard Rule	cannot violate	cannot violate (3)	cannot violate
VM-Host Soft Rule	can violate	can violate (4)	can violate

• VM-VM Affinity Rule : "Keep Virtual Machines Together"
• VM-VM anti-Affinity Rule : "Separate Virtual Machines"
• VM-Host Hard Rule :  "Must run on hosts in group" or "Must Not run on host group"
• VM-Host Soft Rule : "Should run on hosts in group" or "Should Not run on host group"

*1) For example, if a rule is defined to Keep Virtual Machines Together on VM-1 and VM-2 and VM-1 is currently already powered on, an attempt to power on VM-2 will fail if it is registered to a different host. Since vSphere DRS is not activated, the user must manually migrate the VMs to the same host to be able to power on the VM.

*2) For example, a 2-node cluster and a Separate Virtual Machines rule defined to place VM-1 on ESX-01 and VM-2 on ESX-02. ESX-01 experiences a failure and vSphere HA is initiated. vSphere HA is unable to power on VM-1 on ESX-02 as it would violate the rule to keep each virtual machine separate.

*3) For example, if a rule is defined that VM-1 and VM-2 must run on hosts ESX-01 and ESX-02, an attempt to migrate the VMs to hosts outside of the host group is blocked.

*4) For example, if a rule is defined that VM-1 and VM-2 should not run on hosts ESX-03 and ESX-04, an attempt to migrate the VMs to either ESX-03 or ESX-04 is not blocked.

Additional Information

Official Broadcom Documentation :  Using Affinity Rules without vSphere DRS