What Happens If A Drive Fails

hi guys,

im running WHS v1 with 3 drives in a storage pool and thinking of adding a couple more. I was wondering how WHS deals with drive failures...if one of my drives dies does it take the entire pool with it or just the files that resided on it? I am not using data duplication function.

Reason I ask is because I am trying to determine if I should continue with WHS or get a Synology NAS wih RAID 5 capability.

Thanks