options please refer to `mount`(8) manpage. The options are sorted alphabetically
(discarding the 'no' prefix).
+NOTE: most mount options apply to the whole filesystem and only options in the
+first mounted subvolume will take effect. This is due to lack of implementation
+and may change in the future. This means that (for example) you can't set
+per-subvolume 'nodatacow', 'nodatasum', or 'compress' using mount options. This
+should eventually be fixed, but it has proved to be difficult to implement
+correctly within the Linux VFS framework.
+
*acl*::
*noacl*::
(default: on)
A workaround option from times (pre 3.2) when it was not possible to mount a
subvolume that did not reside directly under the toplevel subvolume.
+NOTES ON GENERIC MOUNT OPTIONS
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Some of the general mount options from `mount`(8) that affect BTRFS and are
+worth mentioning.
+
+*noatime*::
+under read intensive work-loads, specifying 'noatime' significantly improves
+performance because no new access time information needs to be written. Without
+this option, the default is 'relatime', which only reduces the number of
+inode atime updates in comparison to the traditional 'strictatime'. The worst
+case for atime updates under 'relatime' occurs when many files are read whose
+atime is older than 24 h and which are freshly snapshotted. In that case the
+atime is updated 'and' COW happens - for each file - in bulk. See also
+https://lwn.net/Articles/499293/ - 'Atime and btrfs: a bad combination? (LWN, 2012-05-31)'.
++
+Note that 'noatime' may break applications that rely on atime uptimes like
+the venerable Mutt (unless you use maildir mailboxes).
+
FILESYSTEM FEATURES
-------------------
projects / platform / upstream / btrfs-progs.git / blobdiff