Enterprise Vault 10.0.3 to 11 Upgrade

Hello Community,

i have a customer project where we want to upgrade the EV 10.0.3 to the new EV 11 version. We have four EV Server which are using the mailarchiving feature with ex 2010 (Cas Array, DAG) and connected to an SQL Cluster. 

Do we need new licence for the upgrade?

Are there main problems which we should be concern about?

Are there certains things that should be prepared on the SQL and EX Server before upgrading?

Are there any big problems with the new EV11 Version?

Thank you very much.