6.5.1

Data Service Rules
Unlike the placement rules, the data service rules do not define storage placement and storage
requirements for the virtual machine. Instead, these rules activate specific data services for the virtual
machine, for example, caching and replication. Storage systems or other entities can provide these
services. They can also be installed on your hosts and vCenter Server. You include the data service rules
in the storage policy components. If the data service is provided by a storage system, you add the
components to the regular rule sets. If the data service is provided by I/O filters, the component is added
to the common rule set.
About Storage Policy Components
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.
n
Compression
n
Caching
n
Encryption
n
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 20‑2. Storage Policy Components
Virtual Machine VM Storage Policy Storage Policy Component
VM1 requires replication every 2 hours SP1 2-hour Replication
VM2 requires replication every 4 hours SP2 (clone of SP1) 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 common rule set of the storage policy.
Components that reference entities other than the I/O filters, for example, a storage system, are added to
regular rule sets with placement rules.
vSphere Storage
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