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Btrfs

A copy-on-write filesystem with snapshots and transparent compression.

Btrfs is a copy-on-write filesystem with snapshots, subvolumes, transparent compression (zstd, zlib, lzo), integrated RAID 0/1/10, and online defragmentation. The on-disk format is based on B-trees, which gives it predictable performance for many workloads while supporting arbitrary file and directory growth without the fragmentation that haunted older filesystems.

Chris Mason started Btrfs at Oracle in 2007, modelled in part on ZFS but with a different licensing strategy that allows it to ship in the mainline Linux kernel. The project has had a long maturation phase — early years had some stability problems — but is now considered production-ready by SUSE, Fedora, Meta, and others who run it at scale.

Btrfs is the default root filesystem on openSUSE Tumbleweed and Fedora Workstation. The snapshot feature is particularly popular for desktop users (snapper integrates with the package manager to take a snapshot before each system update, allowing rollbacks if an update breaks something).

Built into the Linux kernel; userspace tools:
  Debian/Ubuntu: sudo apt install btrfs-progs
  Fedora/RHEL:   sudo dnf install btrfs-progs
  Arch:          sudo pacman -S btrfs-progs