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VM storage policies, used for Storage Policy Based Management (SPBM), are authored by the VMware administrator to describe the desired capabilities when provisioning a VM. The storage and virtualization administrators can discuss policies in advance, ensuring that the Dell Unity system has capability profiles that are compliant with the configured VM storage policies. Any of the capabilities that are included in the capability profiles can be used to create policies. For example, the virtualization administrator can create a policy that will look for the usage tag Database. Any vVol datastores which contain a capability profile that has the usage tag database will be considered compliant. This ensures that any VMs with this storage policy are deployed on the storage pool that the storage administrator has designated for this purpose. Another example is creating a service level with a Platinum policy for when the best performance is required for a VM. When creating a VM storage policy, select EMC.UNITY.VVOL and choose the desired rule as shown in Figure 19.
Low-level storage properties can also be selected when creating VM storage policies. These include characteristics such as drive type, FAST Cache, RAID type, and tiering policy. These are designed to enable advanced VMware administrators who are familiar with storage capabilities to customize their VM storage policies.
The next screen in the wizard displays a list of compatible and incompatible datastores based on the selected capabilities, as shown in Figure 20.
After VM storage policies are configured, VMs can be deployed on vVol datastores similar to NFS and VMFS datastores. On the Select Storage step of the new VM wizard, there is a drop-down menu that displays the VM storage policies that were created in vSphere. When a policy is selected, its capabilities are compared with the capabilities of the available datastores. These datastores are categorized into compatible and incompatible categories to allow the administrator to easily identify datastores that are appropriate for that VM, as shown in Figure 21.
After a VM is deployed using a VM storage policy, vSphere continues to periodically monitor the datastore to ensure continued compliance. The current compliance status and the last-checked date is displayed in the VM Summary page or the VM storage policy Monitor page. You can also initiate an on-demand compliance check on either of these pages. If the datastore falls out of compliance with the specified policy, this is displayed in vSphere Web Client to warn the administrator about the status, as shown in Figure 22.
It is possible to migrate VMs by using Storage vMotion. This provides the ability to move VMs to the datastores with the appropriate capabilities if the requirements change. VMs that have snapshots or fast clones cannot be migrated.
VMs can also be automatically migrated between back-end storage by changing the VM storage policy assigned to that VM. If the new VM storage policy is satisfied by a capability profile within the same vVol datastore, the VM is automatically migrated on the back end to ensure that it resides on a pool with the appropriate capabilities. Migrating the vVol by updating the VM storage policy can only be done if the new policy that you want to use is also available on the same vVol datastore. For example, if a single datastore contains two capability profiles for the Platinum and Bronze service levels, a VM storage profile update can be used to automatically migrate the VM’s vVols from one storage pool to the other.
To edit the VM storage policy assigned to a VM, right-click the VM to open the Manage VM Storage Policies page, as shown in Figure 23.
Because each VM hard disk is stored on individual vVols, you can also apply a different VM storage policy to each individual hard disk. For example, for a database VM, you could put the database hard disk on the Platinum service level and put the log hard disk on the Gold service level.
If the current datastore does not have the required capabilities for the new VM storage policy, a VM storage policy update cannot be made. Instead, use Storage vMotion to migrate the VM to a different vVol datastore that has the appropriate capabilities. To do this, right-click the VM and click Migrate to move the VM to a different storage location. On the Select storage page, there is a drop-down menu for the VM storage policy. You can choose to keep the existing VM storage policy or select a new one on the new datastore. Similar to deploying a new VM, vSphere automatically categorizes the available datastores to help identify which datastores are compatible with this policy, as shown in Figure 24.