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Third-party backup software using VDDK 5.1 may encounter backup/restore failures (2039931)


Third-party backup software using VDDK 5.1 may experience these symptoms:
  • Backup jobs may fail or hang
  • Restore Jobs may fail or hang


This article describes an issue with the VMware Virtual Disk Development Kit (VDDK) that may cause backup and restore operations to hang or fail. Third-party backup vendors that are using the VMware VDDK may encounter backup or restore issues when backing up VMware vSphere environments.


This is a known issue affecting Virtual Disk Development Kit (VDDK) 5.1.

Currently, there is no workaround or resolution available. This article will be updated as information becomes available.

For more information, see the VDDK 5.1 Release Notes, which describes this issue:
Hang in connect or cleanup due to intermittent race condition.

Windows processes can sometimes hang when calling VixDiskLib_ConnectEx() or VixDiskLib_Cleanup() due to a race condition while loading or unloading libraries. There is no known workaround.
For more information on this issue and support, see the vSphere Blog post, Setting the Record Straight on vSphere 5.1 Backup and Recovery Support.

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