Sure! I connected them with a usb adapter with external power source. The power source of the Raspberry Pi alone is not enough to run four disks at the same tim

Sure! I connected them with a usb adapter with external power source. The power source of the Raspberry Pi alone is not enough to run four disks at the same time (at least not for me). For the hard drives I bought a couple of 2.5" disks that I connected to the usb adapter together with my Raspberry Pi. The board runs Debian, and I've setup a RAID 5 system. Then, each of the logical volumes are encrypted with (as?) LUKS. Quite some fun to setup the system, but don't expect any miracles. During a good day I get a read and write speed of roughly 30 mb/s over the home network. Enough for me as a backup system for home usage.