Jetstress tool for Exchange 2013

Greetings

I am upgrading the Exchange 2013 environment and want to run the Jetstress tool before putting the servers in production.

I have 2 Mailbox servers as member of DAG.

Please provide me inputs on below mentioned points:

1. As per microsoft recommendations, the Jetstress tool should be run before installing Exchange Server.

However, i have already installed Exchange server and done the CAS Virtual Directories configuration.

Is it possible if i can run Jetstress after installing Exchange Server.

2. Now, the Exchange is already installed. DO i need to run Jetstress on all DAG members.

Thanks in advance.