Finally, a use for that drawer full of 1 GB USB drives!
When Sun Microsystems was still existing they made a (quite funny) video putting 12 usb sticks in a ZFS pool with RAID: https://constantin.glez.de/2011/01/24/how-save-world-zfs-and...
I would not recommend this setup, Any real drive would be better. I just hated wasting drive bays for the non-critical boot/system partition. In my defense despite burning through many cheap usb drives I have not lost the boot yet, however I do keep a new spare drive taped to the unit.