Installing only the Core packages in Solaris is recommended because minimizing the amount of software on the system minimizes the potential security holes. If you require a GUI on your Solaris platform, need additional functionality, or are new to Solaris, you might consider the End User installation, though it adds over 100 additional packages—exposing your system to far greater risk. I strongly discourage you from using anything but Core.
During the initial installation, you will be asked to partition the hard drive. Here's a recommended approach:
/ (root filesystem): everything else not listed below
swap: the greater of 256 or double the amount of RAM
/var/opt/CPfw1-50: 15GB or a different ...