Hyper‑V Plug‑in Fails with “Failed to Read” Error When Backing Up to a Local VTL (4383239)

Backups using the NetVault Plug‑in for Hyper‑V fail with a “Failed to read” error when the selected backup target is a VTL hosted on the same machine that runs all of the following components:

• Hyper‑V Server
• NetVault Server
• NetVault Plug‑in for Hyper‑V
• VTL device

In this configuration, the Hyper‑V backup consistently fails during the read phase.

The same backup does not fail under the following conditions:

• When QoreStor is selected as the backup target
• When the backup target is a VTL hosted on a different NetVault Server (one that does not run Hyper‑V or the Hyper‑V Plug‑in)

Plug‑in for Filesystem backups complete successfully in the same environment, even when the VTL is hosted on the same machine as:

• • Hyper‑V Server
  • NetVault Server
  • Plug‑in for Hyper‑V

This indicates the issue is specific to the Plug‑in for Hyper‑V when backing up to a local VTL, and does not affect other plug‑ins or targets.

The trace logs show:
BackupStreamContinue - all work is done and the user has been given a send buffer. At 131072
ReadVhd(65536) : FALSE Failed to read.
Error: The parameter is incorrect.