NetWorker: Azure VM Snapshot Backups Fail "Failure when receiving data from the peer(curl error code: 56), Error while copying snapshot to DD"

Summary: NetWorker Azure Virtual Machine (VM) Snapshot backups intermittently fail with the error "Failure when receiving data from the peer(curl error code: 56), Error while copying snapshot to DD." This error appears randomly, during some backups the VM succeeds, on other backups, this failure is observed. ...

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Symptoms

Azure Virtual Machine (VM) backups performed through NetWorker intermittently fail with the following error observed in the backup action log:

207705:nsrazure_save: Curl: Error setting options/performing in curl, error details: Failure when receiving data from the peer(curl error code: 56), Error while copying snapshot to DD
207650:nsrazure_save: azurvmbackup: snapshot VM-NAME_DISK-NAME_SNAPSHOT-TIMESTAMP copy to DD failed
207820:nsrazure_save:Cannot backup to DD.  Backup of saveset: RESOURCE-GROUP-NAME:VM-NAME:VM-NAME_DISK-NAME failed.

Cause

The curl 56 error is a general network connection error code. Common causes are:

  • TLS/SSL handshake issues.
  • Connection reset by peer (server closed the connection unexpectedly).
  • Firewall or security interference.
  • Timeouts or packet loss during data transfer.

The nsrazure_save command is encountering a curl communication issue and aborting the job without retrying the connection. Impacted versions:

  • 19.11.0.x
  • 19.12.0.x
  • 19.13.0.x

Resolution

Retry logic was added to the following NetWorker releases:

  • 19.14.0.0 (January 2026)

 

NOTE: The code change does not resolve the curl connection failure as this is occurring outside of NetWorker. The code change provides "retry" function when this connection issue is encountered. The same "curl error code: 56" messaging may be found in the logs; however you see "Retrying from offset" and the connection resumes. Each save set only attempts to retry 50 times. By default, the NetWorker policy has a "one retry" setting. Meaning, if the save set fails, the policy attempts the back-up again. If the connection fails more than 50 times again, the save set fails to backup. Excessive network connection failures must be investigated at the Azure level.

Additional Information

Example logging with retry logic:

207705:nsrazure_save: Curl: Error setting options/performing in curl, error details: Failure when receiving data from the peer(curl error code: 56), Error while copying snapshot to DD
207705:nsrazure_save: Curl: Error setting options/performing in curl, error details: Failure when receiving data from the peer(curl error code: 56), Error while copying snapshot to DD
207705:nsrazure_save: Curl: Error setting options/performing in curl, error details: Failure when receiving data from the peer(curl error code: 56), Error while copying snapshot to DD
207705:nsrazure_save: Curl: Error setting options/performing in curl, error details: Failure when receiving data from the peer(curl error code: 56), Error while copying snapshot to DD
210931:nsrazure_save: Data transfer failed.  Retrying from offset 74392272896...
210931:nsrazure_save: Data transfer failed.  Retrying from offset 68708990976...
210931:nsrazure_save: Data transfer failed.  Retrying from offset 66345500672...
210931:nsrazure_save: Data transfer failed.  Retrying from offset 78074871808...
In the above example, there are four VM disk save sets backed up in the client. Each save set encountered the curl connection failure and retried from the last offset.

Affected Products

NetWorker

Products

NetWorker Family
Article Properties
Article Number: 000361593
Article Type: Solution
Last Modified: 12 Dec 2025
Version:  5
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