If you don't want greyhole to use your systemdrive (i.e. in case you decide to use the 16GB), you can move them to a larger drive, 1 of the 4 SATA's.I need more specific info on that.If you want to do this you should move your shares to another drive.
I'll link you to another post where that is explained:
http://forums.amahi.org/viewtopic.php?f=39&t=2285
Richard