Home > Storage > PowerMax and VMAX > Data Protection > Dell EMC PowerMax and VMAX All Flash: Snapshot Policies > Default policies
Each array is automatically populated with three default policies: HourlyDefault, DailyDefault, and WeeklyDefault. The default policies can be used with their preset values if they meet the business requirements of applications that are assigned to each policy, and the array resource limits. Otherwise, the RPO rules of the policy should be modified accordingly.
Whether using the default policies as-is, modifying the default policies, or creating policies, you must size the array configuration to meet the expected snapshot usage. The sizing requirements must consider the capacity of the applications that will be protected, the snapshot count, the snapshot retention requirements, and several other capacity- and performance-requirement metrics.
When a policy is modified to reduce the number of snapshots to keep, existing snapshots that exceed the new count are terminated. This action is performed according to the previous count, and not immediately after the count has been reduced. This behavior prevents accidental changes from immediately affecting protection.
Figure 2 is an example of the initial card view of the Snapshot Policies dashboard before SGs have been assigned to the default policies and before any new policies have been created. Figure 3 is the list view of the Snapshot Policies dashboard.
Select the pencil icon as shown on the DailyDefault policy to open a window that displays the parameters of the policy. The parameters can be edited from the resulting window.
The following three figures show the parameters of the default policies. Modifying a policy affects all SGs that are associated with that policy.
The displayed Create a snapshot time adjusts according to the time zone of the user’s local workstation. When the policy is created, the system takes this value and stores it on the array in UTC format.
UTC does not adjust for seasonal time changes. Systems that are in regions where seasonal time changes occur do not automatically adjust the snapshot creation time. Depending on when the policy was created, snapshots may be taken one hour before or one hour after the target time during seasonal time changes.
Whenever possible, create policies with focus on the frequency of snapshots rather than the exact time that the snapshots are taken. This best practice eliminates the need to modify policies during seasonal time changes. This practice is likely to be more acceptable for policies that create snapshots at a high frequency.
For policies that take snapshots at specific times according to business requirements, you may need to modify them to account for seasonal time changes. This requirement is more common for policies that create snapshots at a lower frequency, such as end-of-week or end-of-month processing.