The default file system for the root partition of SUSE Enterprise Linux is Btrfs. So RHEL have stopped supporting it. It is the only filesystem that implements many of the features found in ZFS.
It's also buggy as hell and though I've used SuSE for 17 years I almost stopped this year due to btrfs. Terrible decision from SuSE: but they aren't the company they used to be.
