Avamar: NDMP Dataset Change Forces Level-0 Backup

Unexpected backup behavior when moving NDMP volumes between datasets

Symptoms that may be observed:

• Backup duration is longer than usual.
• A new level 0 (full) backup is triggered instead of an incremental.
• The backup appears to re‑process all files, even though the data already resides in storage.
• Client overtime is required to allow the backup to complete.
• The issue occurs when a volume is moved to a dataset used by a different client.

Impact of Moving NDMP Volumes Between Datasets

When an Avamar NDMP backup runs, the data is linked to the client that initiates the backup, not to the NDMP dataset. This association creates the following conditions that trigger an unexpected full (level 0) backup:

• The volume is moved from one dataset to another while the new dataset is used by a different client.
• The receiving client has never backed up that specific volume before.
• Avamar treats the volume as new data for the client, forcing a level 0 backup regardless of its existing presence in storage.

Consequences of the forced level 0 backup include:

• All files on the volume must be re‑checked and sent to the Avamar NDMP Accelerator, even though the data already resides in the repository.
• The backup duration mirrors that of an initial full backup, which is longer than a level 1 or synthetic full backup.
• Large volumes amplify the time impact, potentially exceeding expected backup windows.

External factors that exacerbate the issue:

• Moving large volumes between clients without adjusting the client’s overtime settings.
• Insufficient client overtime, causing the backup to be interrupted before completion.

Best Practices for Moving NDMP Volumes Between Clients

Primary Recommendation

• Do not move large NDMP volumes between different clients. Keeping the volume on the same client prevents an unnecessary full (level 0) backup.

If a Volume Must Be Moved.

• Schedule additional backup window time for the target client to allow the forced level 0 backup to complete.
• Update the client’s Backup Window in Avamar Administrator:
  • Navigate to Clients → [CLIENT NAME] → Backup Settings.
  • Increase the Maximum Backup Duration or extend the Backup Window to accommodate the extra runtime.
• Verify that the client’s NDMP Dataset is correctly assigned after the move.
• Run a test backup to confirm the new schedule is sufficient.

Verification After Implementation

• Check the backup job log for the new run:
  • Confirm that the backup level is reported as Level 0 (expected after a move).
  • Ensure that the job completes within the extended backup window.
• Validate that subsequent incremental (Level 1) backups run as expected and complete faster.
• Confirm that storage consumption matches expectations (no duplicate full backups).

If you are uncertain about the impact of moving volumes or need assistance extending backup windows, contact Dell Support.