You can't customize your installation. Synology upgrade script will format any drives it finds, unless drive is already formatted according to it's standard version (i.e. /dev/md0 - root, /dev/md1 - swap, /dev/md2+ - data).
Thank you for the fast reply.
But one question remains:
2. Which drive is the best to install the packages on?
When I want to install new Software on my NAS the DSM asks where I want to install it.
i.e.: My Installation of XPEnology is corrupt and I want to have a fresh install.
Do I loose all of my installed Packages?