6.7

Table Of Contents
When you create an anti-affinity rule, it applies to the relevant virtual disks in the datastore cluster. Anti-
affinity rules are enforced during initial placement and Storage DRS-recommendation migrations, but are
not enforced when a migration is initiated by a user.
Note Anti-affinity rules do not apply to CD-ROM ISO image files that are stored on a datastore in a
datastore cluster, nor do they apply to swapfiles that are stored in user-defined locations.
Inter-VM Anti-Affinity
Rules
Specify which virtual machines should never be kept on the same
datastore. See Create Inter-VM Anti-Affinity Rules.
Intra-VM Anti-Affinity
Rules
Specify which virtual disks associated with a particular virtual machine must
be kept on different datastores. See Create Intra-VM Anti-Affinity Rules.
If you move a virtual disk out of the datastore cluster, the affinity or anti-affinity rule no longer applies to
that disk.
When you move virtual disk files into a datastore cluster that has existing affinity and anti-affinity rules, the
following behavior applies:
n
Datastore Cluster B has an intra-VM affinity rule. When you move a virtual disk out of Datastore
Cluster A and into Datastore Cluster B, any rule that applied to the virtual disk for a given virtual
machine in Datastore Cluster A no longer applies. The virtual disk is now subject to the intra-VM
affinity rule in Datastore Cluster B.
n
Datastore Cluster B has an inter-VM anti-affinity rule. When you move a virtual disk out of Datastore
Cluster A and into Datastore Cluster B, any rule that applied to the virtual disk for a given virtual
machine in Datastore Cluster A no longer applies. The virtual disk is now subject to the inter-VM anti-
affinity rule in Datastore Cluster B.
n
Datastore Cluster B has an intra-VM anti-affinity rule. When you move a virtual disk out of Datastore
Cluster A and into Datastore Cluster B, the intra-VM anti-affinity rule does not apply to the virtual disk
for a given virtual machine because the rule is limited to only specified virtual disks in Datastore
Cluster B.
Note Storage DRS rules might prevent a datastore from entering maintenance mode. You can choose to
ignore Storage DRS rules for maintenance mode by enabling the Ignore Affinity Rules for Maintenance
option.
Create Inter-VM Anti-Anity Rules
You can create an anti-affinity rule to indicate that all virtual disks of certain virtual machines must be kept
on different datastores. The rule applies to individual datastore clusters.
Virtual machines that participate in an inter-VM anti-affinity rule in a datastore cluster must be associated
with an intra-VM affinity rule in the datastore cluster. The virtual machines must also comply with the intra-
VM affinity rule.
If a virtual machine is subject to an inter-VM anti-affinity rule, the following behavior applies:
n
Storage DRS places the virtual machine's virtual disks according to the rule.
vSphere Resource Management
VMware, Inc. 114