diff options
author | Dimitri John Ledkov <xnox@ubuntu.com> | 2016-09-08 12:29:10 +0100 |
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committer | Dimitri John Ledkov <xnox@ubuntu.com> | 2016-09-08 12:29:10 +0100 |
commit | 249a3592d5dfdec0e52b5e9e712339364ea758ed (patch) | |
tree | 54a81f37cfdccbb5ba1d3c925e6fd9261311550e /Documentation/btrfs-man5.asciidoc | |
parent | ca0dc13dd212ef8ca19fa6128115fe933b055437 (diff) |
New upstream release. (Closes: #836778)debian/4.7.2-1
Diffstat (limited to 'Documentation/btrfs-man5.asciidoc')
-rw-r--r-- | Documentation/btrfs-man5.asciidoc | 92 |
1 files changed, 90 insertions, 2 deletions
diff --git a/Documentation/btrfs-man5.asciidoc b/Documentation/btrfs-man5.asciidoc index 467f11bf..a1f364e0 100644 --- a/Documentation/btrfs-man5.asciidoc +++ b/Documentation/btrfs-man5.asciidoc @@ -12,9 +12,12 @@ tools. Currently covers: 1. mount options -2. file attributes +2. filesystem features + +3. file attributes + +4. control device -3. control device MOUNT OPTIONS ------------- @@ -406,6 +409,91 @@ NOTE: This option has replaced 'recovery'. Allow subvolumes to be deleted by their respective owner. Otherwise, only the root user can do that. +FILESYSTEM FEATURES +------------------- + +The basic set of filesystem features gets extended over time. The backward +compatibility is maintained and the features are optional, need to be +explicitly asked for so accidental use will not create incompatibilities. + +There are several classes and the respective tools to manage the features: + +at mkfs time only:: +This is namely for core structures, like the b-tree nodesize, see +`mkfs.btrfs`(8) for more details. + +after mkfs, on an unmounted filesystem:: +Features that may optimize internal structures or add new structures to support +new functionality, see `btrfstune`(8). The command *btrfs inspect-internal +dump-super device* will dump a superblock, you can map the value of +'incompat_flags' to the features listed below + +after mkfs, on a mounted filesystem:: +The features of a filesystem (with a given UUID) are listed in +`/sys/fs/btrfs/UUID/features/`, one file per feature. The status of is stored +insid the file. The value '1' is for enabled, '0' means the feature was had +been enabled at the mount time and turned off afterwards. ++ +Whether a particular feature can be turned on a mounted filesystem can be found +in the directory `/sys/fs/btrfs/features/`, one file per feature. The value '1' +means the feature can be enabled. + +List of features (see also `mkfs.btrfs`(8) section 'FILESYSTEM FEATURES'): + +big_metadata:: +(since: 3.4) ++ +the filesystem uses 'nodesize' bigger than the page size +compress_lzo:: +(since: 2.6.38) ++ +the 'lzo' compression has been used on the filesystem, either as a mount option +or via *btrfs filesystem defrag*. + +default_subvol:: +(since: 2.6.34) ++ +the default subvolume has been set on the filesystem + +extended_iref:: +(since: 3.7) ++ +increased hardlink limit per file in a directory to 65536, older kernels +supported a varying number of hardlinks depending on the sum of all file name +sizes that can be stored into one metadata block + +mixed_backref:: +(since: 2.6.31) ++ +the last major disk format change, improved backreferences + +mixed_groups:: +(since: 2.6.37) ++ +mixed data and metadata block groups, ie. the data and metadata are not +separated and occupy the same block groups, this mode is suitable for small +volumes as there are no constraints how the remaining space should be used +(compared to the split mode, where empty metadata space cannot be used for data +and vice versa) ++ +on the other hand, the final layout is quite unpredictable and possibly highly +fragmented, which means worse performance + +no_holes:: +(since: 3.14) +improved representation of file extents where holes are not explicitly +stored as an extent, saves a few percent of metadata if sparse files are used + +raid56:: +(since: 3.9) ++ +the filesystem contains or contained a raid56 profile of block groups ++ +skinny_metadata:: +(since: 3.10) ++ +reduced-size metadata for extent references, saves a few percent of metadata + FILE ATTRIBUTES --------------- The btrfs filesystem supports setting the following file attributes using the |