How to make raid1 more stable - in btrfs or regular markup (ex4 or xfs)?

Question

RAID

Good time of the day. Interested in the stability and performance of the raid1 array in btrfs and conventional markup (xfs or ext4).
For example, the installation in btrfs raid1 went quickly for me, and when I tried to do it in the usual way, xfs raid1, the installation was almost 3-4 times longer.
Can you briefly explain how btrfs works in raid1? And why such a difference in installation time?
My markup is:
/ - xfs (or btrfs)
/home -xfs (or btrfs)
/boot - ext3 or ext4
/boot/efi
/var - xfs (or btrfs)
/usr - xfs (or btrfs)
/var/lib/mysql (can I keep ext4 or xfs?) (or btrfs)
/tmp - xfs (or btrfs)
/backup - xfs (or btrfs)
I have two hard drives, one terabyte each. (WD blue).

Answer 1

RAID1 (with or without any file system) and BtrFS RAID1 are very different things:
A simple RAID1 makes sure that both members are the same - a terabyte on one drive is the same as a terabyte on the other. And this is regardless of whether something is written there or not. Sometimes a bitmap is also used to speed up the initialization process.
To simplify, BtrFS RAID1 only ensures that its data is stored in two copies on different participants. It doesn't need to sync unallocated space.