128 lines
5.3 KiB
ReStructuredText
128 lines
5.3 KiB
ReStructuredText
From kernel 3.3 onwards, BTRFS balance can limit its action to a subset of the
|
|
whole filesystem, and can be used to change the replication configuration (e.g.
|
|
convert data from ``single`` to ``RAID1``).
|
|
|
|
Balance can be limited to a block group profile with the following options:
|
|
|
|
* ``-d`` for data block groups
|
|
* ``-m`` for metadata block groups (also implicitly applies to *-s*)
|
|
* ``-s`` for system block groups
|
|
|
|
The options have an optional parameter which means that the parameter must start
|
|
right after the option without a space (this is mandatory getopt syntax), like
|
|
``-dusage=10``. Options for all block group types can be specified in one command.
|
|
|
|
A filter has the following structure: ``filter[=params][,filter=...]``
|
|
|
|
To combine multiple filters use ``,``, without spaces. Example: ``-dconvert=raid1,soft``
|
|
|
|
BTRFS can have different profiles on a single device or the same profile on
|
|
multiple device.
|
|
|
|
The main reason why you want to have different profiles for data and metadata
|
|
is to provide additional protection of the filesystem's metadata when devices fail,
|
|
since a single sector of unrecoverable metadata will break the filesystem,
|
|
while a single sector of lost data can be trivially recovered by deleting the broken file.
|
|
|
|
Before changing profiles, make sure there is enough unallocated space on
|
|
existing drives to create new metadata block groups (for filesystems
|
|
over 50GiB, this is ``1GB * (number_of_devices + 2))``.
|
|
|
|
Default profiles on BTRFS are:
|
|
|
|
* data: ``single``
|
|
* metadata:
|
|
* single devices: ``dup``
|
|
* multiple devices: ``raid1``
|
|
|
|
|
|
The available filter types are:
|
|
|
|
Filter types
|
|
^^^^^^^^^^^^
|
|
|
|
profiles=<profiles>
|
|
Balances only block groups with the given profiles. Parameters
|
|
are a list of profile names separated by ``|`` (pipe).
|
|
|
|
usage=<percent>, usage=<range>
|
|
Balances only block groups with usage under the given percentage. The
|
|
value of 0 is allowed and will clean up completely unused block groups, this
|
|
should not require any new work space allocated. You may want to use *usage=0*
|
|
in case balance is returning ENOSPC and your filesystem is not too full.
|
|
|
|
The argument may be a single value or a range. The single value ``N`` means *at
|
|
most N percent used*, equivalent to ``..N`` range syntax. Kernels prior to 4.4
|
|
accept only the single value format.
|
|
The minimum range boundary is inclusive, maximum is exclusive.
|
|
|
|
devid=<id>
|
|
Balances only block groups which have at least one chunk on the given
|
|
device. To list devices with ids use :command:`btrfs filesystem show`.
|
|
|
|
drange=<range>
|
|
Balance only block groups which overlap with the given byte range on any
|
|
device. Use in conjunction with ``devid`` to filter on a specific device. The
|
|
parameter is a range specified as ``start..end``.
|
|
|
|
vrange=<range>
|
|
Balance only block groups which overlap with the given byte range in the
|
|
filesystem's internal virtual address space. This is the address space that
|
|
most reports from btrfs in the kernel log use. The parameter is a range
|
|
specified as ``start..end``.
|
|
|
|
convert=<profile>
|
|
Convert each selected block group to the given profile name identified by
|
|
parameters.
|
|
|
|
.. note::
|
|
Starting with kernel 4.5, the ``data`` chunks can be converted to/from the
|
|
``DUP`` profile on a single device.
|
|
|
|
.. note::
|
|
Starting with kernel 4.6, all profiles can be converted to/from ``DUP`` on
|
|
multi-device filesystems.
|
|
|
|
limit=<number>, limit=<range>
|
|
Process only given number of chunks, after all filters are applied. This can be
|
|
used to specifically target a chunk in connection with other filters (``drange``,
|
|
``vrange``) or just simply limit the amount of work done by a single balance run.
|
|
|
|
The argument may be a single value or a range. The single value ``N`` means *at
|
|
most N chunks*, equivalent to ``..N`` range syntax. Kernels prior to 4.4 accept
|
|
only the single value format. The range minimum and maximum are inclusive.
|
|
|
|
stripes=<range>
|
|
Balance only block groups which have the given number of stripes. The parameter
|
|
is a range specified as ``start..end``. Makes sense for block group profiles that
|
|
utilize striping, i.e. RAID0/10/5/6. The range minimum and maximum are
|
|
inclusive.
|
|
|
|
soft
|
|
Takes no parameters. Only has meaning when converting between profiles, or
|
|
When doing convert from one profile to another and soft mode is on,
|
|
chunks that already have the target profile are left untouched.
|
|
This is useful e.g. when half of the filesystem was converted earlier but got
|
|
cancelled.
|
|
|
|
The soft mode switch is (like every other filter) per-type.
|
|
For example, this means that we can convert metadata chunks the "hard" way
|
|
while converting data chunks selectively with soft switch.
|
|
|
|
Profile names, used in ``profiles`` and ``convert`` are one of:
|
|
|
|
* ``raid0``
|
|
* ``raid1``
|
|
* ``raid1c3``
|
|
* ``raid1c4``
|
|
* ``raid10``
|
|
* ``raid5``
|
|
* ``raid6``
|
|
* ``dup``
|
|
* ``single``
|
|
|
|
The mixed data/metadata profiles can be converted in the same way, but conversion
|
|
between mixed and non-mixed is not implemented. For the constraints of the
|
|
profiles please refer to :doc:`mkfs.btrfs` section
|
|
:ref:`PROFILES<man-mkfs-profiles>`.
|