I have PowerEdge 1650 with 3x 18GB  Raid-5 Perc 3di

 

in addition i have 2 spare 18GB harddrives and i'd like to make any some of them.

 

Could somebody give me any idea how?   could i remove one of the raid-5 disks and put that spare one instead and wait for it to rebuild,  then put another spare one.

 

Having two extra rebuilt disks, is there any benefit of it?  for example if all three raid-5 disks fail,  could i install those two rebuilt spare ones and the system would run?