2 sata disks to 1

hi, i have to disks in my oladra but want to remove 1 to use as a usb backup. does anyone know how to do this i.e. can i just plug one out or will i lose data? worth saying that i’m using much less than half the total capacity of the 2 disks together so im hoping that all the files are on disk 1 and i can just pop disk 2 out