What an information lifecycle management policy is

An information lifecycle management (ILM) policy is a set of prioritized ILM rules that determines how the StorageGRID Webscale system manages object data over time.

What proposed, active, and historical policies are

Every StorageGRID Webscale system must have one active ILM policy. A StorageGRID Webscale 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. Activating the proposed policy causes the previously active policy to become a historical policy. Historical ILM policies are those ILM policies that are no longer active. Historical ILM policies cannot be deleted.

conceptual image for ILM policies

How ILM policies evaluate objects

When an object is ingested into the StorageGRID Webscale system, its metadata is evaluated against the first ILM rule in the active ILM policy. If the object metadata matches the filters in the first rule, the content placement instructions for that rule distribute object data to the specified storage locations. If the metadata does not match the filters in the first rule, the object is evaluated against each subsequent ILM rule in the active ILM policy, until a match is made.

One ILM rule must be set as the default ILM rule for the policy. If none of the other ILM rules in the policy matches the object metadata, the placement instructions specified by the default rule are applied. When the StorageGRID Webscale system is first installed, the stock ILM rule, Make 2 Copies, is the default ILM rule.

This figure illustrates how each object is evaluated by the ILM rules in the active ILM policy.

ILM policy logic

ILM policy example

The following figure illustrates an ILM policy that includes ILM rules that specify the following:
  1. When an object is ingested, one copy is placed on disk (Storage Node) at Data Center 1 (DC1), one copy is placed on disk at Data Center 2 (DC2), and one copy is placed on archival media (Archive Node) at DC2.
  2. At the end of one year, the copy on disk at DC2 is deleted.

ILM policy example