...All settings if not defined in config file or as command line options, will be set to it's defaults either as constant values or evaluated from running system.
By default it chooses largest disk for installation. If there are more then one such disk of the same size, it makes RAID array. Separate partitions are used for /boot, and /, and logical volumes for /usr, /var, /tmp and /home. Only minimal disk space are allocated. You should expand (may be done online) logical volumes and file systems when You need to get more disk space. Also there are option to install system into single pre-mount point. ...