Btrfs
Btrfs (pronounced as "better F S", "butter F S", "b-tree F S", or B.T.R.F.S.) is a computer storage format that combines a file system based on the copy-on-write (COW) principle with a logical volume manager (not to be confused with Linux's LVM), developed together. It was founded by Chris Mason in 2007 for use in Linux, and since November 2013, the file system's on-disk format has been declared stable in the Linux kernel.
| Developer(s) | SUSE, Meta, Western Digital, Oracle Corporation, Fujitsu, Fusion-io, Intel, The Linux Foundation, Red Hat, and Strato AG |
|---|---|
| Full name | B-tree file system |
| Introduced | March 23, 2009 with Linux kernel 2.6.29 |
| Partition IDs | |
| Structures | |
| Directory contents | B-tree |
| File allocation | Extents |
| Bad blocks | None recorded |
| Limits | |
| Max volume size | 16 EiB |
| Max file size | 16 EiB |
| Max no. of files | 264 |
| Max filename length | 255 ASCII characters (fewer for multibyte character encodings such as Unicode) |
| Allowed filename characters | All except '/' and NUL ('\0') |
| Features | |
| Dates recorded | Creation (otime), modification (mtime), attribute modification (ctime), and access (atime) |
| Date range | 64-bit signed int offset from 1970-01-01T00:00:00Z |
| Date resolution | Nanosecond |
| Attributes | POSIX and extended attributes |
| File system permissions | Unix permissions, POSIX ACLs |
| Transparent compression | Yes (zlib, LZO and (since 4.14) ZSTD) |
| Transparent encryption | Planned |
| Data deduplication | Yes |
| Copy-on-write | Yes |
| Other | |
| Supported operating systems | Linux, Windows, ReactOS |
| Website | docs |
Btrfs is intended to address the lack of pooling, snapshots, checksums, and integral multi-device spanning in Linux file systems. Chris Mason, the principal Btrfs author, stated that its goal was "to let [Linux] scale for the storage that will be available. Scaling is not just about addressing the storage but also means being able to administer and to manage it with a clean interface that lets people see what's being used and makes it more reliable".