A VM storage policy can include one or several reusable and interchangeable building blocks, called storage policy components. Each component describes a particular data service to be provided for the virtual machine. You can define the policy components in advance and associate them with multiple VM storage policies.

You cannot assign the predefined component directly to a virtual machine or virtual disk. Instead, you must add the component to the VM storage policy, and assign the policy to the virtual machine.

The component describes one type of service from one service provider. The services can vary depending on the providers that you use, but generally belong in one of the following categories.
  • Compression
  • Caching
  • Encryption
  • Replication

When you create the storage policy component, you define the rules for one specific type and grade of service.

The following example shows that virtual machines VM1 and VM2 have identical placement requirements, but must have different grades of replication services. You can create the storage policy components with different replication parameters and add these components to the related storage policies.

Table 1. Storage Policy Components
Virtual Machine Placement Rules Storage Policy Component
VM1 requires replication every 2 hours Virtual Volumes Datastore 2-hour Replication
VM2 requires replication every 4 hours Virtual Volumes Datastore 4-hour Replication

The provider of the service can be a storage system, an I/O filter, or another entity. If the component references an I/O filter, the component is added to the host-based rules of the storage policy. Components that reference entities other than the I/O filters, for example, a storage system, are added to the datastore-specific rule sets.

When you work with the components, follow these guidelines:
  • Each component can include only one set of rules. All characteristics in this rule set belong to a single provider of the data services.
  • If the component is referenced in the VM storage policy, you cannot delete the component. Before deleting the component, you must remove it from the storage policy or delete the storage policy.
  • When you add components to the policy, you can use only one component from the same category, for example caching, per a set of rules.