Rubrik VM backup failing with NFC_COMPRESSION_ERROR and Internal error RBK92010002 (Vmware.UnableFetchDiskData)

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• The Rubrik VM backup solution is failing to successfully back up multiple virtual machines across different hosts. Rubrik support will report following errors , indicating that the backup process is unable to retrieve required disk data from the affected VMs.

Internal error RBK92010002 (Vmware.UnableFetchDiskData)

Rubrik logs :

NfcNewAuthdConnectionEx: Failed to connect: Error reading from vmware-authd socket. Reason: Resource temporarily unavailable NBD_ClientOpen: Couldn't connect to bcn-lx-e######.com:902 DescriptorOpenNbd: Failed to open NBD extent ... NBD_ERR_NETWORK_CONNECT Error 14009 (The server refused connection) Open VMDK failed, err = The server refused connection(err=14009)

VDDK logs :

Failed to create a connection with server bcn-lx-es#######.com: Error reading from vmware-authd socket NBD_ClientOpen: Couldn't connect to bcn-lx-es########.com:902 DiskLib error 2338: NBD_ERR_NETWORK_CONNECT Error 14009 (The server refused connection)

NFC_COMPRESSION_ERROR: Rubrik Logs :

VM W 0:11:32 2025-03-31 19:37:00.746 0:00:00 CREATE_VMWARE_SNAPSHOT_  :::0 [fetch snapshot] [NFC ERROR]NfcAio_TimedWait: The session is in a faulted state: NFC_COMPRESSION_ERROR

VM I 0:11:32 2025-03-31 19:37:00.746 0:00:00 CREATE_VMWARE_SNAPSHOT_  :::0 [fetch snapshot] VixDiskLib: VixDiskLib_Close: Close disk.

VM W 0:11:32 2025-03-31 19:37:00.746 0:00:00 CREATE_VMWARE_SNAPSHOT_ :::0 [fetch snapshot] [NFC ERROR]NfcAio_TimedWait: The session is in a faulted state: NFC_COMPRESSION_ERROR

VM W 0:11:32 2025-03-31 19:37:00.746 0:00:00 CREATE_VMWARE_SNAPSHOT_ :::0 [fetch snapshot] [NFC ERROR]NfcAio_DDBGet: The session is in a faulted state: NFC_COMPRESSION_ERROR

Hostd Log

warning hostd[2100694] [Originator@6876 sub=Libs opID=nbdmode-0000009b67eb11a0] [NFC ERROR]NfcAioGetMessage: Srv invalid msg hdr magic # 4, was expecting -1593779590

warning hostd[2100694] [Originator@6876 sub=Libs opID=nbdmode-0000009b67eb11a0] [NFC ERROR]NfcAioLogFatalSessionErrorLocked: A fatal session error occurred. The error was: 'NFC_SESSION_ERROR' (8

warning hostd[2100694] [Originator@6876 sub=Libs opID=nbdmode-0000009b67eb11a0] [NFC ERROR]NfcAioGetAndProcessMsg: Failed to receive an AIO message: NFC_SESSION_ERROR

warning hostd[2100694] [Originator@6876 sub=Libs opID=nbdmode-0000009b67eb11a0] [NFC ERROR]NfcAioServerProcessMain: Fatal session error. Cleaning up AIO sessio

error hostd[2100694] [Originator@6876 sub=Nfcsvc opID=nbdmode-0000009b67eb11a0] Read error from the nfcLib: NFC_SESSION_ERROR (done = yep)

• Storage Fabric Dropped Frames

2026-07-05T17:58:06.966Z cpu25:2097207)qlnativefc: vmhba65(37:0.1): (0:11) Dropped frame(s) detected (131072 of 131072 bytes).

Environment

• VMware ESXi 7.x
• VMware ESXi 8.x
• Rubrik Back up Solution

Cause

You might notice hosts showing a large number of read error on vmhba1

Might be a Bad SFP in the MDS switch prevented communication with storage array.

Resolution

The storage vendor must be engaged to perform an end-to-end health validation for Array-Side Port Diagnostics, Fabric/physical layer issues & Port Reset and Counter Clearing

Additional Information

Reference:

VM hangs on the host- Dropped Frames

Troubleshooting NFS datastore connectivity issues