If the target server where you install Parallels Pro Control Panel has single and medium capacity hard disks (typically 40 GB and less) the default partitioning scheme of /boot = 50 MB, swap = twice the amount the RAM, and /= rest of the hard disk space will suffice.
However, for disks with a capacity of 40 GB and above or for systems with more than one hard disk, the above scheme is not feasible. In such cases, a custom partitioning scheme must be specified.
If the target server has high capacity hard disks or multiple hard disks, it is recommended that you customize disk partitions so as to have multiple partitions on your hard disks.