path: root/Documentation
diff options
authorQu Wenruo <>2014-06-03 14:20:08 +0800
committerDavid Sterba <>2014-08-22 14:39:33 +0200
commit6c30bee7aa44124892c0c2a7b35a2b5502a28dcf (patch)
tree9e7127b244d197b512ef000fced79fd88bca5576 /Documentation
parent34ca908bad78dd00d62dea4d0a1d90d35e02a2a8 (diff)
btrfs-progs: Documentation: Add filter section for btrfs-balance.
Man page for 'btrfs-balance' mentioned <filters> but does not explain them, which make end users hard to use '-d', '-m' or '-s options. This patch will use the explanations from to enrich the man page. Signed-off-by: Qu Wenruo <> Signed-off-by: David Sterba <>
Diffstat (limited to 'Documentation')
1 files changed, 57 insertions, 3 deletions
diff --git a/Documentation/btrfs-balance.txt b/Documentation/btrfs-balance.txt
index 37d8781e..de93c92f 100644
--- a/Documentation/btrfs-balance.txt
+++ b/Documentation/btrfs-balance.txt
@@ -37,11 +37,11 @@ given balance all chunks in a filesystem.
-act on data chunks
+act on data chunks. See `FILTERS` section for details about <filters>.
-act on metadata chunks
+act on metadata chunks. See `FILTERS` section for details about <filters>.
-act on system chunks (only under -f)
+act on system chunks (only under -f). See `FILTERS` section for details about <filters>.
be verbose
@@ -61,6 +61,60 @@ Show status of running or paused balance.
If '-v' option is given, output will be verbose.
+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: ::
+The available types are: ::
+Balances only block groups with the given replication profiles. Parameters
+are a list of profile names separated by |.
+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.
+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)
+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>.
+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 each selected block group to the given profile name identified by
+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'.
*btrfs balance* returns a zero exist status if it succeeds. Non zero is