[michaelmrose]

I disagree with this statement on multiple fronts. On the first level of the onion RAID1 is for high reliability and BTRFS has historically low reliability but if you peel back that layer you are presenting the ability to transition from BTRFS RAID1 to RAID5 as an appealing feature of BTRFS vs ZFS and yet this just isn't so.

BTRFS has been promising usable RAID5 since 2009 when it was "heading for 1.0" and yet among the most recent developments not but 3 months ago was to add the following warning to btrfs-progs on creation or conversion.

"RAID5/6 support has known problems is strongly discouraged to be used besides testing or evaluation,"

Worse this feature was presented as usable around 2011/12 before being revealed to be unfixably data eating without substantial rewrites in 2016 and 5 years later remains so.

Your hardware might need to be replaced before you can avail yourself of the benefit you posit.

Meanwhile an approach that would actually work on both BTRFS and ZFS would be to add 2 drives to go from RAID1 to RAID10.

The last peel of onion is complaining about down votes. This invites more down votes. If I had to guess people down voted you because you presented a feature that has been a massive pain point for BTRFS as a proposed advantage.