Under certain conditions, VMware backups may prematurely stop reading extents, yet still report success - leading to unexpected results up to and including data loss.


When using NetBackup for VMware to back up very large and/or very fragmented virtual machines (VMs) with BLIB (block level incremental backup) enabled, it is possible that not all of the data will get backed up.  Although the backup and restore may appear to succeed and status code 0 is reported in the Activity Monitor, it may later be discovered that the VM will not boot, or that data files may be missing, inaccurate in size or empty after a restore.


A defect was discovered in a library included in the above versions of NetBackup for VMware.


The formal resolution to this issue (Etrack 2404491) is included in the following release:

  • NetBackup for VMware 7.1 Maintenance Release 1 (

An Emergency Engineering Binary (EEB) bundle is also available for NetBackup for VMware 7.1 by contacting support, referencing this document ID and Etrack 2299772.


Note that applying the maintenance release is the recommended action for this issue, as it contains additional bug fixes and enhancements.

It is strongly recommended that after applying the EEB or maintenance release that new full backups be taken of VMs as soon as possible to mitigate any potential data loss concerns.


Best Practices:
Symantec strongly recommends the following best practices:
1. Always perform a full DR backup prior to making any changes to your environment.
2. Always make sure that your environment is running the latest version and patch level.
3. Perform periodic "test" restores.
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Applies To

What is Affected:

The following versions of NetBackup for VMware have the potential to be affected:

  • 7.0
  • 7.0.1
  • 7.1

How to determine if Affected:

This issue may occur on virtual machines where Changed Block Tracking (CBT) is enabled.

Test restores may fail.  Alternately, test restores may appear to succeed, but files may be missing or have a 0 byte size.  Virtual machines may also fail to boot after the restore is complete.

Terms of use for this information are found in Legal Notices.



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