[In preparation...] Bring as many USB disks you need and a USB hub with enough ports to connect them. Connect them to...
Set them up with linux software RAID, unless you have an ATABeast yourself, otherwise you will not be able to read it.
RAID1 (mirroring): factor 2
RAID5 (striping+parity=recommended): factor (N-1)/N, where N is the number of disks in the set. The larger N, the larger the chance of a failure (and thus of 2 failures at the same time, but the smaller the overhead. N=4-6 is typical).
There's also linux RAID6 (allows for loss of any 2 disks), but I [Michiel] have no experience with that (yet).