Btrfs (B-tree FS, also "Butter FS", "Better FS“) is a copy-on-write (COW) and B-tree file system for the Linux operating system. Btrfs has some overlaps with ZFS and the Apple file system APFS. All data and metadata are managed in tree structures. The Btrfs file system builds on the B-tree structure of the journaling file system XFS and in this respect also shares similarities with Reiser4. Since September 4, 2017, the Brtfs file system has The stadium has been abandoned and is considered to be the future replacement of the widely used ext4 filesystem.With Linux 2.6.29, the Btrfs filesystem has become an integral part of the Linux kernel.
Metadata is of immense importance for any file system. Metadata form the basic information for structuring the file systems. This includes the folder structures, file names, storage locations and access rights for data. The Btrfs file system creates corresponding copies of the metadata on a volume so that in the event of defective hard drives or bad sectors to enable data recovery.
The occurrence of long-term unnoticed errors can lead to damaged data and faulty files in regular storage systems, which can be used without warnings and error messages. To prevent such errors, the Btrfs file system generates checksums for all data and metadata and creates two copies of the metadata. The checksums are checked for each reading process. In the event of deviations, the Btrfs has the option of independently detecting data corruption. By mirroring the metadata, the Btrfs can save the data with the supported RAID levels (RAID 1, RAID 5, RAID 6, RAID 10).
The Btrfs file system has a snapshot function, which enables the point-in-time copy of a complete directory. If data loss or corrupted data in a database results from human error, the snapshot can be used to restore the data from previous times. Due to the copy-on-write processes, the creation of a snapshot requires only a few resources and has little influence on the performance of the system.
Die Netgear ReadyNAS 100, ReadyNAS 300 and ReadyNAS 500 are using an operating system based on Btrfs called "ReadyNAS OS 6".
The following Synology NAS models support the usage of the Btrfs file system:
On August 15, 2014, Thecus announced a firmware update (Thecus OS5 X64 FW 2.06.02.10) to support the Btrfs file system on various Thecus NAS models.