Events causing: Changed block tracking map was changed for volume

[KlausPodolski]

Hello,
I know the question about CBT map changing was part of many topics, but after scanning most of them, I still have no real answer and explanation, why and when this is happening.
During last 2 months I had 3 occasions where Veeam was reporting "Changed block tracking map was changed for volume" and making full long running scan of the backed up volumes:

• Backup device was detached for a couple of weeks from source filesystems
• Upgrade to Windows 23H2 where Veeam Agent is running on
• BIOS settings reset to factory values

For none of them I would expect CBT map changing, since partitions to be backed up neither changed in size nor any other partition layout. So why is this happening and when?

[Mildur]

Hello Klaus

Are you using our CBT driver or the MFT records from Microsoft for CBT?
https://helpcenter.veeam.com/docs/agent ... tml?ver=60

I assume the deep system changes by updating the Microsoft OS will lead to a reset of the volume configuration.
But I don't have an explanation of the other two occurrences. Have you by any chance opened a support case? Veeam Agent Logs and Windows Event Logs should help to find out "the why".

Best,
Fabian

[KlausPodolski]

Hello Fabian,

I have explicitely installed "Changed Block Tracking (CBT) driver" some time ago to improve incremental backup performance. I can see this in the Settings panel of the Control Panel.
The Veeam Agent Logs for the backup job contains warnings like these
Warning Changed block tracking map was changed for volume \\?\Volume{c3a454a2-d5cd-4952-bc08-ed96ea3b8ad8}: current map 57043c23-7afc-11ee-ad7b-806e6f6e6963, previous map 81e19046-5f62-11ee-ad77-806e6f6e6963

The volume ID never changed, but this map id is different and seem be changed on some occasion.
Scanning the log about this new map id, I can see following entry the first time this new map id occuring:

[EpFreeSpaceHelper] Volume ['DATEN_2 (D:)', isSystem=False] length is 8001427603456 bytes. Free space required: 1073741824 bytes
...
[AP] (080c) command: 'Invoke: VeeamVolumeCt.Flush\n{\n (EString) DevicePath = \\?\Volume{c3a454a2-d5cd-4952-bc08-ed96ea3b8ad8}\n}\n'
[AP] (080c) output: <VCPCommandResult result="true" exception="" />
[AP] (080c) output: <VCPCommandArgs><Item key="Generation" type="EGuid" value="{57043c23-7afc-11ee-ad7b-806e6f6e6963}" /><Item key="Index" type="EUInt16" value="2" /></VCPCommandArgs>

It seems that there was happening some flush and new map id (EGuid) was generated. Afterwards the "changed block tracking map was changed" event happend.

[KlausPodolski]

Again, I had the issue "Warning Changed block tracking map was changed for volume" on all my backed up volumes. This time there was only a regular Windows Update inbetween.
If this happens once again I will uninstall Veeam CBT driver since it is really useless and hope, that the MFT detection change is more reliable and stable than that.

[KlausPodolski]

One week later, one backup later, again "Warning Changed block tracking map was changed for volume", that's ridiculous and useless feature. I've uninstalled CBT driver.