How much free space needed on OS drive?

[valdore]

How much space needs to remain free on one's hard drive containing the operating system?

My 750 gig drive has 107 gigs of free space left. At what point do I start storing things on a second drive?

 

[Eraserhead]

10GB maybe?

 

[richard.mac]

ive heard leave 10% of your drive free the let OS X operate at the optimal level. so i would start backing up to an external when youve used 675GB

 

[thejadedmonkey]

OS X'll run with 0 free space. Right now I've got 1.78gb free, and it's by no means ideal, and if I open up some pro apps, it'll give me crap, but it works fine for 99% of things.