Thanks for the sharing and tips.
I never run Full backup on my Veeam Backup job since it is running OK with the Reverse Incremental job.
Or shall I convert the Dedupe backup job into Forever Forward Incremental to get better result in disk space saving instead ?
Forever Forward and Reverse Incremental should give you pretty the same disk space usage. The difference is when the transform happens and how long your snapshot is open on the VM being backed up.
If you aren't doing a periodic full operation on a VM running windows dedupe you are probably never going to be able to avoid the "large increment" problem as you can't cover up the changed blocks from the garbage collection operation with the full.
Running dedupe on production servers really comes down to this for me:
Will it save me a substantial amount of expensive (production) disk space?
Am I willing/able to offset the disk space saved on the expensive disk with additional less expensive (backup) disk space to cover the higher change rate?
In any situation where a VM has an extremely high change rate, from my experience it makes the most sense to run an active full once a week rather than doing transforms because the transform operations take much longer and use more resources than just taking the full does.