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 intra-VM 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 intra-VM anti-affinity rules are defined by default.


In the vSphere Client inventory, right-click a datastore cluster and select Edit Settings.


In the left pane of the Edit Datastore Cluster dialog box, select Rules.


Click Add.


Type a name for the rule.


From the Type menu, select VMDK anti-affinity.


Click Add.


Click Select Virtual Machine.


Select a virtual machine and click OK.


Select at least two virtual disks to which the rule applies and click OK.


Click OK to save the rule.