Veeam B&R limitations for VHDX Live resize usage

Challenge

Live resizing of VHDX files (available in Windows 2012 R2 Hyper-V and later) will be causing following scenarios:

a)  If you shrink the VM disk the backup task for this VM will fail and the following exception can be found in the Agent.<Job name>.Source.<VM name> log file:
[date time] <  6440> cli| VHDX.GetDiskInformation
[date time] <  6440> cli|   (EString) DiskPath = vhdx://<shadowSpec><extent path="full path to the disk" shadow="full path to the disk in the shadow copy" isAutoRecovery="False" /></shadowSpec>
[date time] <  6440> cli|   (EString) Option.Container = {disk}
[date time] <  6440> cli| - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
[date time] <  6440> vhd| Opening VHDX by full path: [full path to the disk].
[date time] <  6440> cli| File 'HostFile{full path to the disk in the shadow copy}' opened (read_only: true, no_cache: false)
[date time] <  6440> dsk| Loading VHDX log.
[date time] <  6440> dsk| Loading VHDX log. Failed.
[date time] <  6440> cli| File 'HostFile{full path to the disk in the shadow copy}' closed
[date time] <  6440> cli| ERR |Failed to process method {VHDX.GetDiskInformation}
[date time] <  6440> cli| >>  |VHDX file was truncated. Current file size: [1503242747904]. Flushed file size: [1825365295104].
[date time] <  6440> cli| >>  |Failed to replay VHDX log.
[date time] <  6440> cli| >>  |--tr:Failed to load VHDX log.
[date time] <  6440> cli| >>  |An exception was thrown from thread [6440].
[date time] <  6440> cli| Trying to poll message from the notification channel (from server side).
[date time] <  6440> net| Triggering AUX channel synchronization. Request id: {guid}
[date time] < 10260> net| Received synchronization response {guid}
[date time] <  6440> cli| No server exception available.
[date time] <  6440> cli| ERR |Failed to process {Invoke} command
[date time] <  6440> cli| >>  |Details:
[date time] <  6440> cli| >>  |VHDX file was truncated. Current file size: [1503242747904]. Flushed file size: [1825365295104].
[date time] <  6440> cli| >>  |Failed to replay VHDX log.
[date time] <  6440> cli| >>  |--tr:Failed to load VHDX log.
[date time] <  6440> cli| >>  |Agent failed to process method {VHDX.GetDiskInformation}.

b) If you expand the VM disk the backup of such a VM may become inconsistent.
 

Cause

After Live resize VHDX metadata is not automatically flushed.

Solution

After performing Shrink of a running virtual machine you should shutdown the VM (not Reboot) and power it on again so that backup job would not fail. However after Expand of a running virtual machine additionally you have to perform new backup for this VM.