An information lifecycle management (ILM) policy is an ordered set of ILM rules that determines how the StorageGRID system manages object data over time.
How an ILM policy evaluates objects
The active ILM policy for your StorageGRID system controls the placement, duration, and data protection of all objects.
- If the filtering criteria for the first rule in the policy match an object's metadata, the object is ingested according to that rule's ingest behavior and stored according to that rule's placement instructions.
- If the filtering criteria for the first rule does not match the object's metadata, the object is evaluated against each subsequent rule in the policy until a match is made.
- If no rules match the object's metadata, the ingest behavior and placement instructions for the default rule in the policy are applied.
Example ILM policy
In this example, all objects belonging to Tenant A are matched by the first rule and are stored as three replicated copies at three data centers. Objects belonging to other tenants are not matched by the first rule, so they are evaluated against the next rule in the policy.
The second ILM rule applies to objects that are larger than 200 KB. These larger objects are stored using erasure coding across three data center sites. Objects 200 KB or smaller are not matched by the second rule, so they are evaluated against the third rule.
The third rule is the default rule for the policy. The default rule is applied to any objects that do not match any other rule in the policy. In this example, the default rule makes two replicated copies of all objects 200 KB or smaller that do not belong to Tenant A.
What proposed, active, and historical policies are
Every StorageGRID system must have one active ILM policy. A StorageGRID system might also have one proposed ILM policy and any number of historical policies.
When you first create an ILM policy, you create a proposed policy by selecting one or more ILM rules and arranging them in a specific order. After you have simulated the proposed policy to confirm its behavior, you activate it to create the active policy.
When you activate a new ILM policy, StorageGRID uses that policy to manage all objects, including existing objects and newly ingested objects. Existing objects might be moved to new locations when the ILM rules in the new policy are implemented.
Activating the proposed policy causes the previously active policy to become a historical policy. Historical ILM policies cannot be deleted.
