[_kdave]

By default the metadata profile is 'DUP' (i.e. 2 copies on one device), the same can be done for data but this reduces the usable capacity. On normal HDD or SSD this should not be needed but having both data and metadata DUP/DUP has been useful on raspberry pi with the micro SD card storage. It's not perfect but increases the chances to get the data back if the card is partially damaged due to power spikes.

[ac29]

I have wondered about this myself - does keeping 2 copies of the same data on a single flash-based drive actually increase reliability? Or is the flash controller going to end up combining the two writes into the same block?