I am going to move my Gen2 drives to the newly purchased 5D.
Obviously, I already have a DroboDashboard on my Mac. It is 2.2.1 for the Dashboard and the firmware is 1.4.2 for the Gen2.
Do I need to install it 2nd time for the 5D?
If I install it again, should the old and the new Drobo Device both be connected to the Mac?
You only need one copy of Dashboard, but you should upgrade to the latest (2.8.2)
To migrate your old diskpack from your Gen2 to the 5D, you need to shutdown cleanly from Dashboard, then move the disks to the 5D (make sure it is powered OFF), and then switch it on and it will migrate. Doesn’t take long
If you want to put some new disks in your old Gen2 and use it as a backup target, you can connect them both, and Dashboard will see both