How SnapVault policies work

Unlike SnapMirror, SnapVault replicates specific Snapshot copies to a destination volume, as defined by a SnapVault policy. It is important to understand how SnapVault policies work if you want to use your own policies instead of the default policies.

Understanding the relationship between Snapshot copy labels and SnapVault policies

A Snapshot policy defines how the system creates Snapshot copies of volumes. The policy specifies when to create the Snapshot copies, how many copies to retain, and how to label them. For example, a system might create one Snapshot copy every day at 12:10 a.m., retain the two most recent copies, and label them "daily".

A SnapVault policy includes rules that specify which labeled Snapshot copies to replicate to a destination volume and how many copies to retain. The labels defined in a SnapVault policy must match one or more labels defined in a Snapshot policy. Otherwise, the system cannot replicate any Snapshot copies.

For example, a SnapVault policy that includes the labels "daily" and "weekly" results in replication of Snapshot copies that include only those labels. No other Snapshot copies are replicated, as shown in the following image:

This illustration shows a Snapshot policy, a source volume, the Snapshot copies created from the Snapshot policy, and then replication of those Snapshot copies to a destination volume based on a SnapVault policy, which specifies replication of Snapshot copies with the "daily" and "weekly" labels.

Default policies and custom policies

The default Snapshot policy creates hourly, daily, and weekly Snapshot copies, retaining six hourly, two daily, and two weekly Snapshot copies.

You can easily use a default SnapVault policy with the default Snapshot policy. The default SnapVault policies replicate daily and weekly Snapshot copies, retaining seven daily and 52 weekly Snapshot copies.

If you create custom policies, the labels defined by those policies must match. You can create custom policies using System Manager.