Home > Storage > PowerMax and VMAX > Data Protection > Dell EMC PowerMax and VMAX All Flash: Snapshot Policies > Snapshot policies overview
Snapshot policies minimize the effort required to maximize application protection. They provide regularly scheduled, crash-consistent snapshots that are based on application requirements.
Snapshot policies create and retain SnapVX snapshots according to the rules within each policy. These customizable rules include the frequency of snapshots, snapshot retention time or count, and compliance-based alerts. Policies are applied to storage groups (SGs) to protect applications with crash-consistent snapshots at regularly scheduled intervals.
Up to four policies can be assigned to each SG. This ability allows applications to be protected with a combination of frequent snapshots and snapshots taken at specified times that are important to the business. There is no limit to the number of SGs that can be assigned to a single policy. Each array supports up to 20 policies.
Child SGs inherit policies that are assigned to its parent SG. This ability enables taking snapshots of an entire database with the option of performing link and restore operations on the entire database or on subsets of a database. When a policy is assigned to a parent SG, the policy takes a snapshot at the parent-SG level and the snapshot is consistent across all child SGs. Conversely, if the policy is individually assigned to each child SG, the child SGs are snapped separately, and the snapshots are not consistent across all child SGs. If a child SG and its parent SG are assigned to the same policy, the policy ignores the child SG.
When assigning parent and child SGs to snapshot policies, be aware of the RPO Interval and Offset values to ensure that the 10-minute minimum RPO is not continually exceeded. This factor must be considered when assigning volumes to multiple SGs. However, users do not have to configure all policies so that snapshots are never taken within 10 minutes of each other. We recommend not intentionally overlapping policies, which would cause applications to be continually snapped every two to three minutes.
Three default policies are automatically populated in the array. These default policies are available for immediate use, but their parameters should be modified according to the requirements of the applications that they will protect. New policies with custom settings can also be created.
Role-based access controls (RBAC) can be implemented, requiring users to have StorageAdmin rights to create, modify, and delete policies, and to associate or disassociate snapshot policies with SGs.