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ISSUE: Fail to connect VM disk by VDDK library. Error=Unknown (VMware VDDK backup)

Reviewed: 28/08/2020

Product Version:

CloudBacko Pro : v4.1 or above

OS: Windows

Problem Description

When performing a VMware guest VM backup in VDDK mode on VMware vCenter / ESXi version 5.0.x, 5.1.x, or 5.5.x, the following error message is received in the backup report:

No. Type Timestamp Log
* info
* erro YYYY/MM/DD hh:mm:ss Fail to connect VM disk by VDDK library “ error: “VDDK Mode Error Virtual Machine = “VM/Hard disk” Reason = “Fail to connect VM disk by VDDK library”. Error=Unknown


This issue occurs because the VMware VDDK 7 API used in CloudBacko Pro v4.1 or above, are not supported by VMware vCenter / ESXi version 5.0.x, v5.1.x, and v5.5.x for backup in VDDK mode.


To workaround this issue, replace the current VDDK 7 API with the VDDK 6 API files, Click Here to download the VDDK v6 API files. Refer to the following steps to replace the files:

  • Stop the CloudBacko Pro service.
  • Stop the CloudBacko Pro NFS service.
  • In Windows Explorer, make a copy of the current folder %CBP_Install_home%\bin\x64.
  • Open the folder %CBP_Install_home\bin\x64.
  • Delete the following .dll files (13 files in total):
  • diskLibPlugin.dll
  • libexpat.dll
  • lookup-types.dll
  • msvcp120.dll
  • msvcr120.dll
  • pcre.dll
  • sqlite3.dll
  • ssoclient.dll
  • vddkVimAccess.dll
  • vim-types.dll
  • vmacore.dll
  • vmomi.dll
  • zlib1.dll
  • Unzip the downloaded file and copy its contents to the %CBP_Install_home%\bin\x64 folder.
  • Restart the CloudBacko Pro service.
  • Restart the CloudBacko Pro NFS service.

After replacing the VDDK 7 API files with the VDDK 6 API files, CloudBacko Pro v4.1 or above can no longer support backup of VMware vCenter / ESXi v7 backup sets. Please replace the files at your own discretion.

Here is the list of VDDK 6 API files (17 files in total):

  • glib-2.0.dll
  • gobject-2.0.dll
  • gthread-2.0.dll
  • gvmomi.dll
  • iconv.dll
  • intl.dll
  • libcurl.dll
  • libeay32.dll
  • liblber.dll
  • libldap.dll
  • libldap_r.dll
  • libxml2.dll
  • ssleay32.dll
  • VddkJNI.dll
  • vixDiskLib.dll
  • vixDiskLibVim.dll
  • vixMntapi.dll
public/edition/cloudbacko_pro/fail_to_connect_vm_disk_by_vddk_library.txt · Last modified: 2021/04/16 17:18 by ronnie.chan