CBT driver volume monitor problem and race condition

[tbsky]

my urbackup server is 2.5.33 at linux.

recently my client windows server 2022 will show notice message below every boot:

“your PC needs to be restarted to finish setting up this device: Volume”

for some reason the server need to reboot every day. sometimes the volume “D:” can not be accessed after boot. then the system can not shutdown and need to reset to become normal.

it bothered me several month. finally I found it is related to urbackup-CBT.

my windows server 2022 is a VM which has three disks. each disk has a partition and formatted as volume “C:”, “D:”, and “S:”. I only want urbackup to backup “C:”. so my related config is below:

List of volumes for which change block tracking should be used (if available) => C
List of volumes for which the change block tracking should be crash persistent => -

I check client side and indeed ubackup shows it only monitors “C:”. ignore “D:” and “S:”

to experiment I remove the urbackup client. and remove all the old backups at server. and try to install 2.5.25-cbt.exe

unfortunately I forgot what version the old urbackup client is. I only know I installed it with msi package. since msi package can not be upgraded cleanly, I just keep using old version.

with 2.5.25-cbt.exe, I found urbackup will monitor all the drives it can found when install. so it will monitor “C:”,“D:”,S:" by default. then the server settings will affect only “C:” drive. although I config server to only monitor “C”. the drive “D:” and “S:” are still monitored.

with old client the setting works. but I wonder how it works. it seems urbackup will monitor all drives at boot then ignore disk “D:” and “S:”. so windows will found new volume every time.

for testing I create another VM with disk “C:” and “D:” and indeed 2.5.24-cbt and 2.5.25-cbt can not change the monitored state of “D:” via server settings.

I don’t now how to debug this. unlike other backup options, I can not easily see the settings at client. is it safe to manually disable CBT via registry key “UpperFilters” under
"HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Enum\STORAGE\Volume"?

is there other registry or config file I can check for CBT settings at client?

thanks a lot for help!

[uroni]

Sorry you are having issues.

If possible could you send me the file at "C:\Program Files\UrBackup\urbackup\data\settings.cfg" that one contains the current client settings.

Also perhaps send/add the (debug) client log as well. See

Having problems with UrBackup? Please read before posting

First of all: Sorry your are having problems with UrBackup. We strive to keep UrBackup bug free, but as with every software project this is a difficult endeavour, which is dependant on the community reporting potential problems. Before you post for help or describe the problem you should check the following: Is there already an ongoing discussion about this problem? Use the forum search functionality. Check the manual and FAQ UrBackup is Open Source. You may be able to fix the problem and p…

for details.

[tbsky]

thank for your reply. I already send the settings file.
check the file it seems settings are there but urbackup client didn’t work as expected.

[uroni]

I see it installing CBT for all volumes directly after install. Then it won’t uninstall once it gets more information from the server from the volumes where there aren’t any file/volume backups.

Should be easy to fix by uninstalling CBT from the volumes without backups as well. Does this sound like it would solve your problem?

[tbsky]

@uroni

I see it installing CBT for all volumes directly after install.

Yes the driver will enable CBT at all volumes when install. if I offline the volume when install urbackup, then CBT will not enable on these offline volumes. and it won’t try to enable CBT again when these volumes are online.

@uroni

Then it won’t uninstall once it gets more information from the server from the volumes where there aren’t any file/volume backups.

That’s interesting. I don’t want to backup the volume so I want CBT disabled. but since I have no backup at the volume, CBT won’t bother to check if it needs enabled/disabled at the volume?

@uroni

Should be easy to fix by uninstalling CBT from the volumes without backups as well. Does this sound like it would solve your problem?

Do you mean edit registry(eg: HKLM\SYSTEM\ControlSet001\Enum\STORAGE\Volume\ ) directly? I can do it manually but it would be better if it can be setup at server. older urbackup will disable the volumes correctly but it seems cause race condition.

I am curious if there is still performance impact(maybe a little) when there is no backup at these CBT-enabled volumes?

Thanks a lot for your help.

[uroni]

@tbsky

Do you mean edit registry(eg: HKLM\SYSTEM\ControlSet001\Enum\STORAGE\Volume\ ) directly? I can do it manually but it would be better if it can be setup at server. older urbackup will disable the volumes correctly but it seems cause race condition.

No that would be the code change (with the next version). I was just wondering if that would fix your issue. Looks like it would.

@tbsky

I am curious if there is still performance impact(maybe a little) when there is no backup at these CBT-enabled volumes?

Yes a small performance impact.

[tbsky]

@uroni

No that would be the code change (with the next version). I was just wondering if that would fix your issue. Looks like it would.

Sorry. I need to make sure the method of “disable CBT”. do you mean modify the registry directly? I haven’t test if the race condition would be fixed after that. currently all volumes are monitored by CBT and there is no race condition.