I have 9.8 with existing data
1. I want to to convert aggergate to NAE, it has volumes that are not encrypted
2. I am confused, i thought you can just convert the aggrigate with one command

storage aggregate modify -aggregate aggregate_name -node node_name -encrypt-with-aggr-key true

It failed and I found one MDV_aud vilume which I encrypted and the aggegate conversion fails

1. Do I have to convert all volumes to NVE to encrypt the aggigate to NAE

This link says that I will loose the dedup

It is 2 years old, is it current?

If you have existing aggregates with data on them, enabling NAE isn’t as simple as just switching it on. Every volume in the aggregate needs to be encrypted with NVE first, then you can enable NAE on the aggregate. But, if the aggregate is NAE, and all the volumes are NVE, well, you won’t get those aggregate deduplication savings (which was probably the main reason for enabling NAE in the first place.)

NetApp Aggregate Encryption: Some Examples and Some Questions Answered