RAID Array

Hi, im familiar enough with RAID and its operations. My question is this. I have just inherited a server with both the o.s. and data all running off a raid 5 array. Im happy enough with this fault tolerance but am concerned that perhaps the o.s. should be on raid 1 array (separate from the data). There will be a lot of work involved in changing this and was wondering will i notice any performance increase if i decide to separate the o.s. and data onto two different arrays.

Thanks