You can create a VMDK anti-affinity rule for a virtual machine that indicates which of its virtual disks must be kept on different datastores.

VMDK anti-affinity rules apply to the virtual machine for which the rule is defined, not to all virtual machines. The rule is expressed as a list of virtual disks that are to be separated from one another.

If you attempt to set an VMDK anti-affinity rule and an intra-VM affinity rule for a virtual machine, vCenter Server rejects the most recently defined rule.

If a virtual machine is subject to a VMDK anti-affinity rule, the following behavior applies:

  • Storage DRS places the virtual machine's virtual disks according to the rule.
  • Storage DRS migrates the virtual disks using vMotion according to the rule, even if the migration is for a mandatory reason such as putting a datastore in maintenance mode.
  • If the virtual machine's virtual disk violates the rule, Storage DRS makes migration recommendations to correct the error or reports the violation as a fault if it cannot make a recommendation that will correct the error.

No VMDK anti-affinity rules are defined by default.


  1. Browse to the datastore cluster in the vSphere Client.
  2. Click the Configure tab and click Configuration.
  3. Select VM/Host Rules.
  4. Click Add.
  5. Type a name for the rule.
  6. From the Type menu, select VMDK anti-affinity.
  7. Click Add.
  8. Click Select Virtual Machine.
  9. Select a virtual machine and click OK.
  10. Select at least two virtual disks to which the rule applies and click OK.
  11. Click OK to save the rule.