/dev/hda1               Gentoo /boot, GRUB      ext3       64M  GRUB chainloads Windows, boots Gentoo kernel(s) from /dev/hda1, Ubuntu kernel/initrd from /dev/hda6 (Ubuntu shouldnt install nor manage a bootloader!)
/dev/hda2               Windows XP Pro          ntfs       10G  Needs Office, VS.Net,...
/dev/hda3               Shared                  fat32       2G  Transfer files between Windows and Linux

/dev/hda4               Extended
        /dev/hda5       Gentoo /                ext3      512M  /bin, /lib, /mnt, /root, /sbin
        /dev/hda6       Ubuntu / (incl. /boot)  ext3      512M  /boot(!!), /bin, /lib, /mnt, /root, /sbin
        
        /dev/hda7       vg-system                               10G extra in here
                /dev/vg-system-swap             swap        1G  Might be less (1G RAM)
                
                /dev/vg-system-gentoo_opt       jfs         1G  Grow when necessary
                /dev/vg-system-gentoo_usr       jfs         2G  Grow when necessary
                /dev/vg-system-gentoo_var       xfs         1G  Grow when necessary

                /dev/vg-system-ubuntu_opt       jfs         1G  Grow when necessary, might be too big
                /dev/vg-system-ubuntu_usr       jfs         3G  Grow when necessary
                /dev/vg-system-ubuntu_var       jfs       512M  Grow when necessary, might be insufficient (what does Ubuntu place under /var?)
                
        /dev/hda8       vg-data
                /dev/vg-data-home               jfs         1G  Grow when necessary
                /dev/vg-data-tmp                xfs       512M  Grow when necessary
                /dev/vg-data-media              jfs         1G  Grow when necessary

                Optional:
                /dev/vg-data-jhbuild            jfs         3G  JHBuild, shared between Gentoo and Ubuntu

                                                           ---
Total:                                                     27G (37G with complete vg-system)
                                                           80G total -> 40G extra for vg-data