ch-fs-limits.rst

maximum file name length

255

This limit is imposed by Linux VFS, the structures of BTRFS could store larger file names.

maximum symlink target length

depends on the nodesize value, for 4KiB it's 3949 bytes, for larger nodesize it's 4095 due to the system limit PATH_MAX

The symlink target may not be a valid path, i.e. the path name components can exceed the limits (NAME_MAX), there's no content validation at :manref:`symlink(3)` creation.

maximum number of inodes

2⁶⁴ but depends on the available metadata space as the inodes are created dynamically

Each subvolume is an independent namespace of inodes and thus their numbers, so the limit is per subvolume, not for the whole filesystem.

inode numbers

minimum number: 256 (for subvolumes), regular files and directories: 257, maximum number: (2⁶⁴ - 256)

The inode numbers that can be assigned to user created files are from the whole 64bit space except first 256 and last 256 in that range that are reserved for internal b-tree identifiers.

maximum file length

inherent limit of BTRFS is 2⁶⁴ (16 EiB) but the practical limit of Linux VFS is 2⁶³ (8 EiB)

maximum number of subvolumes

the subvolume ids can go up to 2⁴⁸ but the number of actual subvolumes depends on the available metadata space

The space consumed by all subvolume metadata includes bookkeeping of shared extents can be large (MiB, GiB). The range is not the full 64bit range because of qgroups that use the upper 16 bits for another purposes.

maximum number of hardlinks of a file in a directory

65536 when the extref feature is turned on during mkfs (default), roughly 100 otherwise and depends on file name length that fits into one metadata node

minimum filesystem size

the minimal size of each device depends on the mixed-bg feature, without that (the default) it's about 109MiB, with mixed-bg it's is 16MiB