btrfs (often pronounced "better fs") has quite a few features that ext4 lacks.
However, comparing the functionality of btrfs vs ext4, what is lacking in btrfs?1
In other words, what can I do with ext4 that I can't with btrfs?
1 Ignoring the lesser battle-ground testing of btrfs given ext4 is so widely used
Best Answer
Disadvantages of btrfs compared to ext4:
btrfs doesn't support badblocks
This means that if you've run out of spare non-addressable sectors that the HDD firmware keeps to cover for a limited number of failures, there is no way to mark blocks bad and avoid them at the filesystem level.
Swap files are only supported via a loopback device, which complicates things because it seems impossible to resume from suspend using this method
It's quite tricky to calculate free space, so much so that...
You can get "No space left on device" errors even though btrfs' own tools say there is space