Disk expansion trigger a full (incremental) backup

[daw_idee]

Hello,
we have a large fileserver (20tb) (vm on vmware) backed up via veeam agent, the backup is configured as foward incremental, a full initial backup and then always incremental backups, today we have expanded the disk on the vm, tonight the backup has begun and it show the warning "Disk 1 layout change detected, resetting changed block tracking for all volumes on this disk".

Usually the backup completes in 10 minutes and the transfered data is about 20 GB, today the backup needs to transfer at this moment 2tb and going...
The data on the source volume hasn't changed so much in a day, and going at this pace will fill the repository shortly, on the repo the files is a vib.

I've read some topics about this behavior and someone says: " it wont do to full backup" others say the opposite, but in my case it's making a full backup for sure.
the question is I can't expand the fileserver volume without trigger a full backup?
thanks
best regards

[daw_idee]

i've noticed that from the inventory the machine I can select "install driver" CBT.

[Mildur]

Hi D.G.

The CBT Driver will be used for detecting changed blocks. When veeam runs the backup job, the CBT driver tells Veeam which blocks on the disk has changed since the last backup run. The Agent will then only read this changed blocks instead of the entire disk. This will speed up synthetic fulls and incremental backups. We recommend to install our CBT Driver.

When you resize a disk, the CBT Data is resetting automatically. Our Agent will then have to backup the entire disk again.
It's a full backup of the entire disk, but stored as an incremental backup file (*.vib).

Thanks
Fabian

[daw_idee]

Hello Fabian, thanks for the reply, so in this case the only solution to not trigger a new full backup is add a new disk to the vm instead of expand it?
thanks

[Mildur]

Your welcome.
Yes, a new disk will not reset the CBT data of another disk.

If I may, I recommend to have always the space for 1-2 additional full backups (without Fast Cloning).
For example corrupted, Backup Chains may need a new Active Full. Or if you restore a backup as a new VM. It will be an active Full because the ID has changed.