Ted Ts’o sent out the EXT4 updates today for Linux 6.11. He explained in that pull request:
“Many cleanups and bug fixes in ext4, especially for the fast commit feature. Also some performance improvements; in particular, improving IOPS and throughput on fast devices running Async Direct I/O by up to 20% by optimizing jbd2_transaction_committed().”
Yes, because it doesn’t do as much to protect you from data corruption.
If you have a use case where a barely-measurable increase in speed is essential, but not so essential that you wouldn’t just pay for more RAM to keep it in cache, and also it doesn’t matter if you get the wrong answer because you’ve not noticed the disk is failing, and you can afford to lose everything in the case of a power cut, then sure, use a legacy filesystem. Otherwise, use a modern one.
Ext4 is not legacy, just because something newer is out there. Ext4 is proven and rock solid, not without reason the standard for most Linux systems. It doesn’t randomly corrupt your files. If someone would read your reply, one would think that Ext4 is abandoned since decades and a risk to use.
If one has to ask and don’t understand Btrfs, should just use Ext4 by default; a safe and good option without risking anything. There are no downsides to this. Use Btrfs only, if you know what you are doing, if you understand it and actually need the extra functionality.
And, may I add, if your chosen distro defaults to it.
But ext4 is a journaling filesystem, so a power cut shouldn’t harm it.