Data Domain: Using MTree Replication for the "backup" MTree

Applies To:

• All Data Domain systems
• All DD OS releases

Support Statement

MTree replication cannot be configured with the "backup" MTree as the destination.

The reason is a core requirement of MTree replication:

• The destination MTree must not already exist at the time replication is configured.

The "backup" MTree is a special, system‑defined MTree that:

• Exists by default on every Data Domain system
• Cannot be deleted or re-created

Because it always exists, it cannot be used as a destination for MTree replication.

Recommended Alternative

If replication of data stored under /backup is required:

1. Create one or more new MTrees on the source Data Domain system.
2. Copy or migrate data from the backup MTree into the newly created MTrees.
3. Configure MTree replication using these new MTrees as the replication sources, targeting newly created MTrees on the destination system.

This approach is fully supported.

Using "backup" as a Replication Source - Limitations

Although the "backup" MTree can technically be used as a source for MTree replication (with a differently named destination MTree), this configuration is not recommended.

Reason:

• The "backup" MTree is the only MTree that supports directory replication.
• If the backup MTree is used as an MTree replication source, directory replication cannot be configured on that system in the future.

This restriction can limit replication design flexibility and impact future configuration options.

REFERENCE

• Data Domain: MTree Replication FAQs | Frequently Asked Questions.