mirror of
https://github.com/koverstreet/bcachefs-tools.git
synced 2025-02-24 00:00:19 +03:00
34 lines
1.4 KiB
ReStructuredText
34 lines
1.4 KiB
ReStructuredText
Device labels and targets
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
By default, writes are striped across all devices in a filesystem, but
|
|
they may be directed to a specific device or set of devices with the
|
|
various target options. The allocator only prefers to allocate from
|
|
devices matching the specified target; if those devices are full, it
|
|
will fall back to allocating from any device in the filesystem.
|
|
|
|
Target options may refer to a device directly, e.g.
|
|
``foreground_target=/dev/sda1``, or they may refer to a device label. A
|
|
device label is a path delimited by periods - e.g. ssd.ssd1 (and labels
|
|
need not be unique). This gives us ways of referring to multiple devices
|
|
in target options: If we specify ssd in a target option, that will refer
|
|
to all devices with the label ssd or labels that start with ssd. (e.g.
|
|
ssd.ssd1, ssd.ssd2).
|
|
|
|
Four target options exist. These options all may be set at the
|
|
filesystem level (at format time, at mount time, or at runtime via
|
|
sysfs), or on a particular file or directory:
|
|
|
|
.. container:: description
|
|
|
|
| ``foreground_target``: normal foreground data writes, and metadata
|
|
if
|
|
| ``metadata_target`` is not set
|
|
|
|
``metadata_target``: btree writes
|
|
|
|
``background_target``: If set, user data (not metadata) will be moved
|
|
to this target in the background
|
|
|
|
``promote_target``: If set, a cached copy will be added to this
|
|
target on read, if none exists |