btrfs-progs/Documentation/btrfs-balance.asciidoc

btrfs-balance(8)
================

NAME
----
btrfs-balance - balance btrfs filesystem

SYNOPSIS
--------
*btrfs balance* <subcommand> <args>

DESCRIPTION
-----------
*btrfs balance* is used to balance chunks in a btrfs filesystem across
multiple or even single device.

See `btrfs-device`(8) for more details about the effect on device management.

NOTE: The balance subcommand also exists under the *filesystem* namespace. This
still works for backward compatibility but is deprecated and should not be
used anymore.

NOTE: A short syntax *btrfs balance <path>* works due to backward compatibility
but is deprecated and should not be used anymore. Use *btrfs balance start*
command instead.

SUBCOMMAND
----------
*cancel* <path>::
Cancel running or paused balance.

*pause* <path>::
Pause running balance.

*resume* <path>::
Resume interrupted balance.

*start* [options] <path>::
Balance chunks across the devices *online*.
+
Balance and/or convert (change allocation profile of) chunks that
passed all filters in a comma-separated list of filters for a
particular chunk type.
If filter list is not given balance all chunks of that type.
In case none of the -d, -m or -s options is
given balance all chunks in a filesystem.
+
`Options`
+
-d[<filters>]::::
act on data chunks. See `FILTERS` section for details about <filters>.
-m[<filters>]::::
act on metadata chunks. See `FILTERS` section for details about <filters>.
-s[<filters>]::::
act on system chunks (only under -f). See `FILTERS` section for details about <filters>.
-v::::
be verbose
-f::::
force reducing of metadata integrity

*status* [-v] <path>::
Show status of running or paused balance.
+
If '-v' option is given, output will be verbose.

FILTERS
-------
From kernel 3.3 onwards, btrfs balance can limit its action to a subset of the
full filesystem, and can be used to change the replication configuration (e.g.
moving data from single to RAID-1). This functionality is accessed through the
'-d', '-m' or '-s' options to btrfs balance start, which filter on data,
metadata and system blocks respectively.

A filter has the following stucture: ::
'type'[='params'][,'type'=...]

The available types are:

*profiles*::
Balances only block groups with the given replication profiles. Parameters
are a list of profile names separated by |.

*usage*::
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 space allocated. You may want to use usage=0 in
case balance is returnin ENOSPC and your filesystem is not too full.

*devid*::
Balances only block groups which have at least one chunk on the given
device (by btrfs device ID -- use btrfs fi show to list device IDs)

*drange*::
Balances 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*::
Balances 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*::
Convert each selected block group to the given profile name identified by
parameters.

*limit*::
Process only given number of chunks, after all filters apply. 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.

*soft*::
Takes no parameters. Only has meaning when converting between profiles.
When doing convert from one profile to another and soft mode is on,
restriper won't touch chunks that already have the target profile. This is
useful if e.g. half of the FS was converted earlier.
+
The soft mode switch is (like every other filter) per-type. This means
that we can convert for example meta chunks the "hard" way while converting
data chunks selectively with soft switch.

Profile names, used in profiles and convert are one of: 'raid0', 'raid1',
'raid10', 'raid5', 'raid6', 'dup', 'single'.

EXIT STATUS
-----------
*btrfs balance* returns a zero exit status if it succeeds. Non zero is
returned in case of failure.

AVAILABILITY
------------
*btrfs* is part of btrfs-progs.
Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for
further details.

SEE ALSO
--------
`mkfs.btrfs`(8),
`btrfs-device`(8)