Btrfs is a great filesystem for proxmox in raid 1. Stop telling people not to use it
Btrfs gets a bad rap sometimes but I have been using it for years and it works very well. It is able to take failing hardware and power outages and still has good performance.
My anecdotal experience with btrfs is that it constantly broke in raid 1, no problems with any other filesystems on the exact same hardware and setup. YMMV