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author | Dimitri John Ledkov <xnox@ubuntu.com> | 2018-01-11 15:44:55 +0000 |
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committer | Dimitri John Ledkov <xnox@ubuntu.com> | 2018-01-11 15:44:55 +0000 |
commit | d78d642bffff6ea49d62c19f26052ed6d3dcc467 (patch) | |
tree | db0f470018ee6f4b93fb8fd601401fa157e5dbe3 /Documentation/btrfs-balance.asciidoc | |
parent | b309a4dfbe8130b9fef087df59dd18a487a9c18e (diff) |
New upstream release.
Diffstat (limited to 'Documentation/btrfs-balance.asciidoc')
-rw-r--r-- | Documentation/btrfs-balance.asciidoc | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/Documentation/btrfs-balance.asciidoc b/Documentation/btrfs-balance.asciidoc index cc81de91..7017bed7 100644 --- a/Documentation/btrfs-balance.asciidoc +++ b/Documentation/btrfs-balance.asciidoc @@ -21,8 +21,8 @@ filesystem. The balance operation is cancellable by the user. The on-disk state of the filesystem is always consistent so an unexpected interruption (eg. system crash, reboot) does not corrupt the filesystem. The progress of the balance operation -is temporarily stored and will be resumed upon mount, unless the mount option -'skip_balance' is specified. +is temporarily stored as an internal state and will be resumed upon mount, +unless the mount option 'skip_balance' is specified. WARNING: running balance without filters will take a lot of time as it basically rewrites the entire filesystem and needs to update all block pointers. @@ -201,10 +201,11 @@ ENOSPC ------ The way balance operates, it usually needs to temporarily create a new block -group and move the old data there. For that it needs work space, otherwise -it fails for ENOSPC reasons. +group and move the old data there, before the old block group can be removed. +For that it needs the work space, otherwise it fails for ENOSPC reasons. This is not the same ENOSPC as if the free space is exhausted. This refers to -the space on the level of block groups. +the space on the level of block groups, which are bigger parts of the filesytem +that contain many file extents. The free work space can be calculated from the output of the *btrfs filesystem show* command: @@ -227,7 +228,7 @@ space. After that it might be possible to run other filters. Conversion to profiles based on striping (RAID0, RAID5/6) require the work space on each device. An interrupted balance may leave partially filled block -groups that might consume the work space. +groups that consume the work space. EXAMPLES -------- @@ -238,7 +239,7 @@ can be found in section 'TYPICAL USECASES' of `btrfs-device`(8). MAKING BLOCK GROUP LAYOUT MORE COMPACT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The layout of block groups is not normally visible, most tools report only +The layout of block groups is not normally visible; most tools report only summarized numbers of free or used space, but there are still some hints provided. @@ -298,7 +299,7 @@ data to the remaining blockgroups, ie. the 6GiB are now free of filesystem structures, and can be reused for new data or metadata block groups. We can do a similar exercise with the metadata block groups, but this should -not be typically necessary, unless the used/total ration is really off. Here +not typically be necessary, unless the used/total ratio is really off. Here the ratio is roughly 50% but the difference as an absolute number is "a few gigabytes", which can be considered normal for a workload with snapshots or reflinks updated frequently. |