I know this topic is coming up over and over again.
I know we can use nbudeployutil to calculate the capacity used, as well as take the weekly/monthly full backup to generate client report, and sum it manually.
Here is my senerio: Yesterday i backup large 20TB file from clientA to retention 5yrs. After backup completed, I delete this 19TB from clientA and and continue backup 1TB in standard policy. After 90 days, when I do self audit,will this 19TB still shown in report? Coz FETB license is calculate the average over 90 days.
No it will not, nbdeployutil is based on maximum backup image sizes during the reporting window, not average sizes. In you case it will revert to 1 TB after 90 days.
I think this is covered in NBU Admin Guide Vol 2 which you should always consut when using nbdeployutil along with the notes in the output XLS as manual adjustments may well be required.
Best regards, Andrew