Symptoms

The error might be reported one time after running a VADP backup for a set with the CBT and "Verify disks signature on the next backup" options enabled.


Cause

1. The hotadd transport method is used during backup and the DS-Client is installed in a Windows virtual machine.

How to identify the transport method used during VADP backup:

- In DS-User > Logs > Activity Log, hightlight the intended backup activity

- click on "Event Log" button

- look for an entry like "Reading 'disk-nr.vmdk' using transport mode 'certain-transport mode ' (vm_name)", for example: Reading 'disk2000.vmdk' using transport mode 'hotadd' (w2k12r2-vm1)" or "Reading 'disk2000.vmdk' using transport mode 'nbdssl' (w2k12r2-vm1)".


2. There is a data block signature mismatch in a generation of a file already backed up, as a result the next generation backed up will be a master (this will be saved online during the first backup session after the one that reported the error).


Workaround

1. According to VDDK programming guide, it is recommended to disable the automount option for the Windows DS-Client computer (if hotadd mode is taken use of).

Disabling Automount in Windows DS-Client computer

When using HotAdd transport from a Windows DS-Client, it can make unwanted changes to HotAdded volumes. To prevent this, Windows automount should be disabled on the Windows DS-Client computer.

To disable Windows automount:


//Start DiskPart by opening an elevated command prompt window and typing the commmand below:

C:\> diskpart


//Disable automounting:

DISKPART> automount disable


//Prevent any previously mounted volumes from being re-mounted the next time.

DISKPART> automount scrub


//Exit DiskPart.

DISKPART> exit


2. No action required. If there is low bandwidth between DS-Client and DS-System and the VADP sets that reported the error protects very large virtual machines, you may consider suspending the original set and create a new one with initial backup feature enabled.

Also as a best practice, lock the backup transport mode to nbdssl.