When you create an ILM rule, you specify whether StorageGRID should protect objects at ingest using the Dual commit, Balanced, or Strict options. Depending on your choice, StorageGRID makes interim copies and queues the objects for ILM evaluation later, or uses synchronous placement and makes copies to meet ILM requirements immediately.
- Dual commit: When you select Dual commit, StorageGRID immediately makes interim object copies on two different Storage Nodes and returns an "ingest successful" message to the client. The object is queued for ILM evaluation and copies that meet the rule's placement instructions are made later.
Dual commit provides a quick response to clients so that StorageGRID is able to handle subsequent requests more promptly, and the redundant interim copies protect data against the loss of a Storage Node before ILM can be evaluated. However, if the interim copies do not meet the rule's placement instructions, Dual commit is less efficient as StorageGRID must create, track, and delete object copies that are ultimately not required.
- Strict: When you select the Strict option, StorageGRID uses synchronous placement on ingest and immediately makes all object copies specified in the rule's placement instructions. If it is not possible to create these copies, for example because a required storage location is temporarily unavailable, ingest fails. The client must retry the operation later.
The Strict option ensures that objects are always offered the protection against loss that is specified in the rule's placement instructions. For example, objects can be protected against the failure of more than one Storage Node or against the complete failure of an entire site, if those protections are present in the rule. However, when using the Strict option you must be prepared for a higher level of ingest failure, as transient issues can make creating all required copies temporarily impossible.
- Balanced: When you select the Balanced option, StorageGRID also uses synchronous placement on ingest and immediately makes all copies specified in the rule's placement instructions. In contrast with the Strict option, if it is not possible to immediately make these copies StorageGRID instead uses Dual commit.
The Balanced option provides high levels of data security, grid performance, and ingest success. Ingest can take longer, because StorageGRID might need to create erasure coded objects or remote copies before it can return an "ingest successful" message to the client.
Using the Balanced option is recommended unless you have a specific operational reason to make a different selection.
