PowerProtect: VM Backups Fail with VDDK Error: 14009 Due to NBD Transport Issues

Summary: Virtual machine (VM) backups fail with VDDK error 14009 (server-refused connection) and NFC_NETWORK_ERROR. The cause is Network Block Device (NBD) transport sessions that fail back from HotAdd, and network‑connect errors. ...

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Symptoms

The export of the backup session log shows:

...
YYYY-MM-DD HH:MM:SS NOTICE: [bb9a93bbba9726f5;ae0318f83d5f1ee4] Opened handle to virtual disk '[MY_DATASTORE_NAME] MY_VM_NAME/MY_VM_NAME_1.vmdk' using 'nbdssl' transport mode. Requested mode was 'nbdssl'. Hotadd transport available.
...
YYYY-MM-DD HH:MM:SS WARN:   [bb9a93bbba9726f5;ae0318f83d5f1ee4] Data Mover: Hard disk 2: VDDK: Retrying read request ...
YYYY-MM-DD HH:MM:SS ERROR:  [bb9a93bbba9726f5;ae0318f83d5f1ee4] Data Mover: Hard disk 2: VDDK: Unable to read 2048 sectors starting at sector 52207616.  VDDK Error: 14009: The server refused connection.
YYYY-MM-DD HH:MM:SS ERROR:  [bb9a93bbba9726f5;ae0318f83d5f1ee4] Data Mover: Hard disk 2: VDDK: Reading data not successful.
YYYY-MM-DD HH:MM:SS DEBUG:  [bb9a93bbba9726f5;ae0318f83d5f1ee4] New status Disk Mover Status: 2001, "Hard disk 2", "Failure", "Reading data not successful.  Unable to read 2048 sectors starting at sector 52207616.  VDDK Error: 14009: The server refused connection.", Error: Reading data not successful.  Unable to read 2048 sectors starting at sector 52207616.  VDDK Error: 14009: The server refused connection.
YYYY-MM-DD HH:MM:SS ERROR:  [bb9a93bbba9726f5;ae0318f83d5f1ee4] Unable to backup virtual disk "Hard disk 2".
...

The Support bundle VM Direct Engine /opt/emc/vproxy/runtime/logs/vbackupd-vddk.log shows:

YYYY-MM-DD HH:MM:SS NOTICE: VDDK INFO DISKLIB-LIB   : RWv failed ioId: #53088717 (2338) (34) .
YYYY-MM-DD HH:MM:SS NOTICE: VDDK WARN [NFC ERROR]NfcAio_TimedWait: The session is in a faulted state: NFC_NETWORK_ERROR
YYYY-MM-DD HH:MM:SS NOTICE: VDDK INFO VixDiskLib: Detected DiskLib error 2338 (NBD_ERR_NETWORK_CONNECT).
YYYY-MM-DD HH:MM:SS NOTICE: VDDK INFO VixDiskLib: VixDiskLib_Read: Read 2048 sectors at 52207616 failed. Error 14009 (The server refused connection) (DiskLib error 2338: NBD_ERR_NETWORK_CONNECT) at 7738.
YYYY-MM-DD HH:MM:SS NOTICE: VDDK INFO VixDiskLib: VixDiskLib_Close: Close disk.
YYYY-MM-DD HH:MM:SS NOTICE: VDDK WARN [NFC ERROR]NfcAio_TimedWait: The session is in a faulted state: NFC_NETWORK_ERROR

Cause

There is a significant number of NBD transport sessions being used during the scheduled backup execution. The HotAdd transport mode is recommended for large workloads to minimize the TCP\IP network traffic during the scheduled execution.

Resolution

Deploy at least one VM Direct Engine for every cluster in the vSphere environment.
The default Hot Add, Failback to Network Block Device setting should then be changed to HotAdd to have the backups only use the HotAdd transport.

Additional Information

Review the Transport mode considerations section of the PowerProtect Data Manager Virtual Machine User Guide for further insight. The most recent versions of the product documentation are available for download on the PowerProtect Data Manager Drivers & Downloads page. 

Article Properties
Article Number: 000221905
Article Type: Solution
Last Modified: 26 Feb 2026
Version:  3
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