new to Mac world

Hey guys,


I am still waiting for my rmbp order status to change from that ugly "processing" to something else.
Meanwhile I had a couple of questions regarding the mac OS as this would be my first ever mac after probably 15 years of windows use.
I am used to creating a primary partition in windows usually C which i only use for the OS and installed programmes only, and creating another drive usually D for saving my photos/music/videos etc. I do this so that I do not lose my data in case of windows crashing or any similar issue or if i need to fresh install the OS i donot have to copy everything again.
now, my question is do i need to do the same in OSX ? or I would be fine with just one drive, because it pains me when i have to build a computer from scratch.
How do you guys manage your macs when it comes to disc drives and partitions. I might also be installing windows so i know i will have to create a separate partition for that but my primary concern is managing the OS and data separately.