G-raid drive set up keeps coming unmounted


 I have a  G-raid 4TB setup of two, 2TB drives hooked up to a mac.   The G-raid set up keeps coming unmounted from the mac.  At that point you have to use a restore program to access the information on the G-raid, or you wipe and start over.   Since I backup in triplicate it's easy to put the information back on the drive, but it kind of defeats the purpose.   I have set the computer to not put the hard drive to sleep, but I can't figure out how to stop.  Please help.