Avamar: Backup Failures Caused by Isilon Configuration Issues and Stale Sessions

Summary: Avamar backup failures can stem from Isilon configuration: snapshot incremental backup not enabled, DMA is not set to generic, or Network Data Management Protocol (NDMP) sessions that stop responding. ...

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Symptoms

Avamar Backup Failure Indicators

Avamar backup does not complete successfully.

  • The backup job finishes with an error status.
  • No data is transferred to the Isilon storage.
  • Backup logs report a failure without an obvious Isilon related cause.

Cause

Potential Factors Leading to Avamar Backup Failures from the Isilon Side.

Snapshot‑based Incremental Backup Not Enabled

If the volume designated for backup does not have the BACKUP_MODE variable set to SNAPSHOT, Avamar cannot perform snapshot‑based incremental backups.
The NDMP service then attempts a full backup, which often exceeds time or space limits and results in failure.

 

Incorrect Data Management Application (DMA) Setting

The NDMP global configuration includes a DMA parameter. The DMA must be set to generic for Avamar to recognize it. The NDMP service cannot correctly coordinate with Avamar if the DMA is not recognized.
This causes backup attempts to end prematurely.


Stale NDMP Backup Sessions

Residual NDMP sessions that remain active after a backup interruption occupy resources and lock the backup path. Subsequent backup attempts encounter session conflicts, leading to failure until the stale sessions are cleared.

Resolution

Enable Snapshot‑Based Incremental Backups on Isilon. 

Confirm that the backup volume is configured for snapshot‑based incremental backups. If it is not, enable the setting.

# List current NDMP settings for the backup path
isi ndmp settings variables list --path=/path/to/backup/

 

If the BACKUP_MODE variable is missing or set to a value other than SNAPSHOT, create or update it:

# Create the BACKUP_MODE variable with SNAPSHOT value
isi ndmp settings variables create --path=/path/to/backup/ --name=BACKUP_MODE --value=SNAPSHOT

 

Set the Correct Data Management Application (DMA)

Avamar requires the DMA setting to be generic. Verify and correct this value if necessary.

# View global NDMP settings
isi ndmp settings global view

 

Locate the line that begins with DMA:. If it shows anything other than generic, modify it:

# Set DMA to generic
isi ndmp settings global modify --dma=generic

 

Remove Stale NDMP Backup Sessions.

Stale sessions can block new backups, so list the current sessions and delete any that are stale.

# List all NDMP sessions
isi ndmp sessions list

 

Identify sessions with a status indicating that they are stale, then delete those that are found.

# Delete a specific stale session (replace  with the actual ID)
isi ndmp sessions delete --session=

 

Verification Steps

  • Run a manual Avamar backup for the affected volume.
  • Confirm that the backup completes without errors in the Avamar console.
  • Rerun "isi ndmp sessions list" to ensure that no new stale sessions appear.
  • Check the Avamar logs for entries confirming snapshot‑based incremental processing.
NOTE: If the issue persists after completing these steps, contact Dell Support with the relevant logs and session identification.
CAUTION: Changing BACKUP_MODE or the DMA setting affects all NDMP clients that use this Isilon node. Ensure that no other critical NDMP backups are running before making changes.
CAUTION: Deleting active NDMP sessions may interrupt in‑progress backups. Verify that the sessions are truly stale before removal.

Affected Products

Avamar, Avamar Server, Isilon
Article Properties
Article Number: 000068243
Article Type: Solution
Last Modified: 22 Dec 2025
Version:  5
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