[rleigh]

Note it won't necessarily halve the capacity. Selectively enable it for the datasets requiring it, and avoid the overhead with the rest.

[bestham]

No but parity archives solves a different problem, with only some percent of wasted storage you can survive bit-errors in your dataset. It's like reed-solomon for files.

In order to achive the same with ZFS you have to run RAID-Z2 on sparse files.