Overview
| Parameter | ZFS | Btrfs |
|---|---|---|
| Type | FS + Volume Manager | File System (CoW) |
| License | CDDL | GPL (Mainline Kernel) |
| RAID 5/6 | Stable (RAIDZ) | Unstable (Write hole) |
| Compression | LZ4, GZIP, ZSTD | LZO, zlib, ZSTD |
| Resizing | Rigid (vdev based) | Flexible (online add/remove) |
ZFS (OpenZFS) is a mature storage management system combining a file system and a logical volume manager. It focuses on data integrity and scalability. Btrfs (B-Tree FS) is a modern Linux file system using Copy-on-Write (CoW) to ensure fault tolerance and simplify administration.
Performance
ZFS utilizes the ARC (Adaptive Replacement Cache) algorithm, which is significantly more efficient than the standard Linux Page Cache when sufficient RAM is available. In read operations, ZFS outperforms Btrfs due to intelligent caching. Btrfs performs better on SSDs in scenarios involving small files and fast snapshots, but performance degrades with heavy fragmentation typical of databases and VM images.
Configuration & complexity
ZFS requires managing pools and virtual devices (vdevs). Pool creation command: zpool create mypool raidz1 /dev/sda /dev/sdb /dev/sdc. Once a vdev is created, you cannot add a single disk to expand it (only replace all disks or add a new vdev). Btrfs allows dynamic device management: btrfs device add /dev/sdd /mnt/data followed by btrfs balance start /mnt/data.
When to choose what
- ZFS: Enterprise storage, NAS (TrueNAS), servers with mission-critical data where RAIDZ stability and protection against silent data corruption are paramount.
- Btrfs: Desktop PCs (Fedora, openSUSE), Docker containers (via efficient subvolumes), systems with mixed-size drives requiring frequent configuration changes.
Cost / licensing
ZFS is distributed under the CDDL license, which prevents its direct inclusion in the Linux kernel (except for distributions like Ubuntu using DKMS modules). Btrfs is part of the vanilla Linux kernel (GPL), simplifying support and updates without third-party repositories.
Ecosystem & integrations
ZFS is the standard for FreeBSD and is widely used in Solaris-like systems. On Linux, it requires zfsutils-linux. Btrfs is supported by all modern distributions out-of-the-box and integrated into management tools like Snapper for automatic system rollbacks.
Verdict
Choose ZFS for servers and RAID arrays where reliability and caching speed outweigh expansion flexibility. Choose Btrfs for workstations and flexible cloud environments where native kernel support and easy storage resizing are required.