You're advised to install your distribution (/ [root]) in a partition of its own, roughly 15 - 30 GiB should be reserved for it, in case your system crashes, your personal files will remain intact.
I use 5 Gb for the root partition. All the programs I need are installed. That leaves me over 900 Mb free for additional programs additional and enough room for updates (pisi packages are downloaded in /var/cache/pisi/packages).
SWAP should be twice the size of your RAM
This rule is not relevant anymore, now that we have several gigabite of RAM on the average PC. For example, I have 2 Gb of RAM and no swap partition at all. Swapping slows down the PC, because data transfer is slower on the harddrive than on the RAM.
Your should split the remaing space between two partitions, one (/home) being your default home directory, and the other a backup to /home so that files can be recovered in case of an incident or if you need an older version of a file you editted.
This seems a bit complex and resssource consuming (automatic synchronisation) to me.
Are you talking about RAID ?