Earlier quoted context omitted.
par2 is very limited. It only support 32k parts in total (or in reality that means in practice 16k parts of source and 16k parts of parity). Lets take 100GB of data (relatively large, but within realm of reason of what someone might want to protect), that means each part will be ~6MB in size. But you're thinking you also created 100GB of parity data (6MB*16384 parity parts) so you're well protected. You're wrong. Now…
what other tool do you recommend?
we can't have nice things