Common rules are based on data services that are generic for all types of storage and do not depend on a datastore. These additional services become available in the VM Storage Policies interface when you install third-party I/O filters developed through vSphere APIs for I/O Filtering. You can reference these data services in a VM storage policy.
Unlike storage-specific rules, common rules do not define storage placement and storage requirements for a virtual machine, but ensure that additional data services, such as I/O filters, become enabled for the virtual machine. No matter which datastore the virtual machine runs on, the enabled filters can provide the following services:
Caching. Configures a cache for virtual disk data. The filter can use a local cache or a flash storage device to cache the data and increase the Input/Output Operations Per Second and hardware utilization rates for the virtual disk.
Replication. Replicates virtual machine or virtual disks to external targets such as another host or cluster.
For more information about I/O filters, see Filtering Virtual Machine I/O.