84 lines
4.0 KiB
ReStructuredText
84 lines
4.0 KiB
ReStructuredText
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From kernel 3.3 onwards, btrfs balance can limit its action to a subset of the
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whole filesystem, and can be used to change the replication configuration (e.g.
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moving data from single to RAID1). This functionality is accessed through the
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*-d*, *-m* or *-s* options to btrfs balance start, which filter on data,
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metadata and system blocks respectively.
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A filter has the following structure: *type[=params][,type=...]*
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The available types are:
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profiles=<profiles>
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Balances only block groups with the given profiles. Parameters
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are a list of profile names separated by "*|*" (pipe).
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usage=<percent>, usage=<range>
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Balances only block groups with usage under the given percentage. The
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value of 0 is allowed and will clean up completely unused block groups, this
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should not require any new work space allocated. You may want to use *usage=0*
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in case balance is returning ENOSPC and your filesystem is not too full.
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The argument may be a single value or a range. The single value *N* means *at
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most N percent used*, equivalent to *..N* range syntax. Kernels prior to 4.4
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accept only the single value format.
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The minimum range boundary is inclusive, maximum is exclusive.
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devid=<id>
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Balances only block groups which have at least one chunk on the given
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device. To list devices with ids use **btrfs filesystem show**.
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drange=<range>
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Balance only block groups which overlap with the given byte range on any
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device. Use in conjunction with *devid* to filter on a specific device. The
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parameter is a range specified as *start..end*.
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vrange=<range>
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Balance only block groups which overlap with the given byte range in the
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filesystem's internal virtual address space. This is the address space that
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most reports from btrfs in the kernel log use. The parameter is a range
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specified as *start..end*.
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convert=<profile>
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Convert each selected block group to the given profile name identified by
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parameters.
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.. note::
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Starting with kernel 4.5, the *data* chunks can be converted to/from the
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*DUP* profile on a single device.
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.. note::
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Starting with kernel 4.6, all profiles can be converted to/from *DUP* on
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multi-device filesystems.
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limit=<number>, limit=<range>
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Process only given number of chunks, after all filters are applied. This can be
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used to specifically target a chunk in connection with other filters (*drange*,
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*vrange*) or just simply limit the amount of work done by a single balance run.
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The argument may be a single value or a range. The single value *N* means *at
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most N chunks*, equivalent to *..N* range syntax. Kernels prior to 4.4 accept
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only the single value format. The range minimum and maximum are inclusive.
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stripes=<range>
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Balance only block groups which have the given number of stripes. The parameter
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is a range specified as *start..end*. Makes sense for block group profiles that
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utilize striping, ie. RAID0/10/5/6. The range minimum and maximum are
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inclusive.
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soft
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Takes no parameters. Only has meaning when converting between profiles.
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When doing convert from one profile to another and soft mode is on,
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chunks that already have the target profile are left untouched.
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This is useful e.g. when half of the filesystem was converted earlier but got
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cancelled.
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The soft mode switch is (like every other filter) per-type.
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For example, this means that we can convert metadata chunks the "hard" way
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while converting data chunks selectively with soft switch.
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Profile names, used in *profiles* and *convert* are one of: *raid0*, *raid1*,
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*raid1c3*, *raid1c4*, *raid10*, *raid5*, *raid6*, *dup*, *single*. The mixed
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data/metadata profiles can be converted in the same way, but it's conversion
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between mixed and non-mixed is not implemented. For the constraints of the
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profiles please refer to ``mkfs.btrfs(8)``, section *PROFILES*.
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