depending on disk activity, and how stuffed the drive is, it'll take longer.. i've had it take 5-6 days before for 200gb
if you can spare the time, next time you reboot at the console, go into the array card bios where you can look at the status (it'll show you a percentage of how much it's done) and just let it sit there. no activity means it'll go a lot faster
if you cancel the job, you might be ok but probably not. if you rip the drive out, you'll ruin your container. it's probably already relying on these new drives