Error: VDDK NOT_REACHED filtlib_error.h:82 causes intermittent third-party backup failures
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Error: VDDK NOT_REACHED filtlib_error.h:82 causes intermittent third-party backup failures

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Article ID: 411638

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Updated On:

Products

VMware vCenter Server

Issue/Introduction

  • Third-party backup software reports intermittent failures when backing up virtual machines.
  • The error "NOT_REACHED bora/lib/public/filtlib_error.h:82" appears in backup software logs.
  • The software reports "VMware Virtual Disk Development Kit unrecoverable error."
  • The Virtual Disk Development Kit (VDDK) component crashes when accessing VM disk data.
  • Backups fail randomly for individual VMs during snapshot operations.
  • The same VM often backs up successfully on retry without any changes.

These failures disrupt your backup schedules. The backup process terminates with various error codes depending on your backup software.

This error appears in your backup software logs on the backup server or media server. The exact log location varies by backup vendor.

Example from NetBackup:

  • Windows: `C:\Program Files\Veritas\NetBackup\logs\`
  • Linux: `/usr/openv/netbackup/logs/`

Check your backup software documentation for specific log locations. This error does NOT appear in VMware logs (vCenter Server, ESXi, or VM logs).

Additional symptoms reported:

  • Random VM backup failures across different VMs
  • Subsequent backup attempts complete successfully
  • Backup occurs during snapshot or disk access operations
  • No corresponding errors in vSphere infrastructure

Environment

  • ESXi 8.0 Update 3 hosts with vCenter Server management.
  • Third-party backup software uses VDDK for agentless VM backups.

Cause

The "NOT_REACHED" error indicates an internal assertion failure in the VDDK library. This component is embedded in third-party backup software. The assertion at line 82 of filtlib_error.h should never execute under normal conditions.

VMware environmental factors that may contribute to this issue:

  • High CPU oversubscription causes scheduling delays
  • Network buffer depletion affects connections
  • Extended operation times stress session management
  • Storage latency variations during disk access

The "bora" path identifies VMware's internal VDDK code. Successful retries indicate an edge-case condition rather than an infrastructure problem.

Resolution

For Backup Software Resolution:

Check for available updates first.

Your backup vendor may have already resolved this compatibility issue in a newer version or patch.

Contact your backup software vendor to:

  • Verify you have the latest software version or patches
  • Check their known issues database for this error
  • Confirm compatibility with ESXi 8.0 Update 3
  • Request VDDK updates if available
  • Configure retry and timeout settings
  • Explore alternative transport modes (NBD, HotAdd) as a workaround

Backup vendors regularly update their products to address VDDK compatibility. This issue may already have a hotfix or be resolved in current releases.

VMware Environment Optimization:

While waiting for vendor resolution, these VMware environment adjustments may reduce occurrence:

  1. Reduce vCPU oversubscription:
    • Monitor current ratios using vCenter Server performance charts
    • Target below 200% oversubscription for backup infrastructure
    • Consider dedicated resources for backup proxy VMs

  2. Optimize network performance:
    • Check for "OutOfBuffers" conditions in ESXi logs
    • Increase network buffer sizes where needed
    • Review network adapter settings

  3. Monitor storage performance:
    • Keep latency below 15 milliseconds during backup windows
    • Use vCenter Server storage performance metrics
    • Consider dedicated datastores for backup operations

  4. Schedule considerations:
    • Avoid backup operations during maintenance windows
    • Stagger workloads to reduce resource contention
    • Monitor resource usage patterns in vCenter Server

Additional Information

VMware Documentation:

Important Notes:

  • VDDK is embedded in third-party backup software and updated through vendor releases
  • Backup vendors maintain compatibility matrices and release notes for VMware environments
  • Your vendor may offer multiple transport modes that could work around this issue
  • Some vendors provide diagnostic tools to test VDDK functionality

The "bora" directory in the error is VMware's internal naming convention. This represents an internal assertion failure within the VDDK library component. These libraries are used within the vendor software, thus contact with the vendor is the essential step to resolving these issues.

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