btrfs-progs: docs: updates
- group features on status page - update developer docs - add cross references Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba
parent
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@ -13,7 +13,7 @@ in meeting your performance expectations for your specific workload.
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Combination of features can vary in performance, the table does not
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cover all possibilities.
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**The table is based on the latest released linux kernel: 6.4**
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**The table is based on the latest released linux kernel: 6.5**
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The columns for each feature reflect the status of the implementation
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in following ways:
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@ -43,26 +43,34 @@ in following ways:
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- Stability
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- Performance
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- Notes
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* - :doc:`discard (synchronous)<Trim>`
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* - :doc:`Subvolumes, snapshots<Subvolumes>`
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- :statusok:`OK`
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- OK
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-
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- mounted with `-o discard` (has performance implications), also see `fstrim`
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* - :doc:`discard (asynchronous)<Trim>`
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- :statusok:`OK`
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-
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- mounted with `-o discard=async` (improved performance)
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* - Autodefrag
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- :statusok:`OK`
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-
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-
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* - :doc:`Defrag<Defragmentation>`
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- :statusmok:`mostly OK`
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-
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- extents get unshared (see below)
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* - :doc:`Compression<Compression>`
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- :statusok:`OK`
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-
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-
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* - :doc:`Checksumming algorithms<Checksumming>`
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Defragmentation<Defragmentation>`
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- :statusmok:`mostly OK`
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-
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- extents get unshared (see below)
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* - :ref:`Autodefrag<mount-option-autodefrag>`
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- :statusok:`OK`
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-
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-
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* - :doc:`Discard (synchronous)<Trim>`
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- :statusok:`OK`
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-
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- mounted with `-o discard` (has performance implications), also see `fstrim`
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* - :doc:`Discard (asynchronous)<Trim>`
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- :statusok:`OK`
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-
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- mounted with `-o discard=async` (improved performance)
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* - :doc:`Out-of-band dedupe<Deduplication>`
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- :statusok:`OK`
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- :statusmok:`mostly OK`
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@ -71,10 +79,14 @@ in following ways:
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- :statusok:`OK`
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- :statusmok:`mostly OK`
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- (reflink), heavily referenced extents have a noticeable performance hit (see below)
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* - :doc:`More checksumming algorithms<Checksumming>`
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* - :doc:`Filesystem resize<Resize>`
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- :statusok:`OK`
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- OK
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-
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- shrink, grow
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* - :doc:`Device replace<Volume-management>`
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- :statusmok:`mostly OK`
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- mostly OK
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- (see below)
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* - :doc:`Auto-repair<Auto-repair>`
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- :statusok:`OK`
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- OK
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@ -87,18 +99,66 @@ in following ways:
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- :statusmok:`mostly OK`
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- mostly OK
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-
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* - :ref:`Degraded mount<mount-option-degraded>`
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- :statusok:`OK`
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- n/a
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-
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* - :doc:`Balance<Balance>`
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- :statusok:`OK`
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- OK
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- balance + qgroups can be slow when there are many snapshots
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* - :doc:`Send<Send-receive>`
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Receive<Send-receive>`
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- :statusok:`OK`
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- OK
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-
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* - Offline UUID change
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- :statusok:`OK`
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- OK
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-
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* - Metadata UUID change
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Seeding<Seeding-device>`
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Quotas, qgroups<Qgroups>`
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- :statusmok:`mostly OK`
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- mostly OK
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- qgroups with many snapshots slows down balance
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* - :doc:`Swapfile<Swapfile>`
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- :statusok:`OK`
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- n/a
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- with some limitations
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* - nodatacow
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Device replace<Volume-management>`
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* - :doc:`Subpage block size<Subpage>`
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- :statusmok:`mostly OK`
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- mostly OK
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- (see below)
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* - Degraded mount
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- :statusok:`OK`
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- n/a
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-
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- Also see table below for more detailed compatibility.
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* - :doc:`Zoned mode<Zoned-mode>`
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- :statusmok:`mostly OK`
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- mostly OK
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- Not yet feature complete but moderately stable, also see table below
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for more detailed compatibility.
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Block group profiles
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^^^^^^^^^^^^^^^^^^^^
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.. list-table::
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:header-rows: 1
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* - Feature
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- Stability
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- Performance
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- Notes
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* - :ref:`Single (block group profile)<mkfs-section-profiles>`
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- :statusok:`OK`
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- OK
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@ -131,50 +191,59 @@ in following ways:
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- :statusunstable:`unstable`
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- n/a
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- (see below)
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* - Mixed block groups
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* - :ref:`Mixed block groups<mkfs-feature-mixed-bg>`
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Filesystem resize<Resize>`
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- :statusok:`OK`
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- OK
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- shrink, grow
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* - :doc:`Balance<Balance>`
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- :statusok:`OK`
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- OK
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- balance + qgroups can be slow when there are many snapshots
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* - Offline UUID change
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On-disk format
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^^^^^^^^^^^^^^
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Features that are typically set at *mkfs* time (sometimes can be changed or
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converted later).
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.. list-table::
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:header-rows: 1
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* - Feature
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- Stability
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- Performance
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- Notes
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* - :ref:`extended-refs<mkfs-feature-extended-refs>`
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- :statusok:`OK`
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- OK
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-
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* - Metadata UUID change
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* - :ref:`skinny-metadata<mkfs-feature-skinny-metadata>`
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Subvolumes, snapshots<Subvolumes>`
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* - :ref:`no-holes<mkfs-feature-no-holes>`
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Send<Send-receive>`
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* - :ref:`Free space tree<mkfs-feature-free-space-tree>`
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Receive<Send-receive>`
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* - :ref:`Block group tree`<mkfs-feature-block-group-tree>`
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Seeding<Seeding-device>`
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Quotas, qgroups<Qgroups>`
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- :statusmok:`mostly OK`
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- mostly OK
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- qgroups with many snapshots slows down balance
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* - :doc:`Swapfile<Swapfile>`
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- :statusok:`OK`
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- n/a
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- with some limitations
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Interoperability
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^^^^^^^^^^^^^^^^
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Integration with other Linux features or external systems.
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:doc:`See also<Interoperability>`.
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.. list-table::
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:header-rows: 1
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* - Feature
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- Stability
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- Performance
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- Notes
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* - :ref:`NFS<interop-nfs>`
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- :statusok:`OK`
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- OK
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@ -183,10 +252,6 @@ in following ways:
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- :statusok:`OK`
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- OK
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- IO controller
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* - :ref:`Samba<interop-samba>`
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- :statusok:`OK`
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- OK
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- compression, server-side copies, snapshots
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* - :ref:`io_uring<interop-io-uring>`
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- :statusok:`OK`
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- OK
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@ -199,35 +264,10 @@ in following ways:
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- :statusok:`OK`
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- OK
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-
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* - :ref:`Free space tree<mkfs-feature-free-space-tree>`
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- :statusok:`OK`
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-
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-
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* - Block group tree
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- :statusok:`OK`
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-
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-
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* - :ref:`no-holes<mkfs-feature-no-holes>`
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* - :ref:`Samba<interop-samba>`
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- :statusok:`OK`
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- OK
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-
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* - :ref:`skinny-metadata<mkfs-feature-skinny-metadata>`
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- :statusok:`OK`
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- OK
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-
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* - :ref:`extended-refs<mkfs-feature-extended-refs>`
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- :statusok:`OK`
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- OK
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-
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* - :doc:`Subpage block size<Subpage>`
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- :statusmok:`mostly OK`
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- mostly OK
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- Also see table below for more detailed compatibility.
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* - :doc:`Zoned mode<Zoned-mode>`
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- :statusmok:`mostly OK`
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- mostly OK
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- Not yet feature complete but moderately stable, also see table below
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for more detailed compatibility.
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- compression, server-side copies, snapshots
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Please open an issue if:
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@ -256,7 +296,7 @@ with subpage or require another feature to work:
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- The max_inline mount option value is ignored, as if mounted with max_inline=0
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* - Free space cache v1
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- :statusunsupp:`unsupported`
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- Free space tree is mandatory, v1 has some assumptions about page size
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- Free space tree is mandatory, v1 makes some assumptions about page size
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* - Compression
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- :statusok:`partial support`
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- Only page-aligned ranges can be compressed
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@ -303,12 +343,6 @@ are unaffected by the zoned device constraints.
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* - Free space tree
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- :statusok:`supported`
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-
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* - single profile
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- :statusok:`supported`
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- Both data and metadata
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* - DUP profile
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- :statusok:`partial support`
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- Only for metadata
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* - Filesystem resize
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- :statusok:`supported`
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-
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@ -150,6 +150,33 @@ DATA STRUCTURES AND DEFINITIONS
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__u64 rsv_excl;
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};
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.. _struct_btrfs_ioctl_fs_info_args:
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.. code-block:: c
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/* Request information about checksum type and size */
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#define BTRFS_FS_INFO_FLAG_CSUM_INFO (1 << 0)
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/* Request information about filesystem generation */
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#define BTRFS_FS_INFO_FLAG_GENERATION (1 << 1)
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/* Request information about filesystem metadata UUID */
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#define BTRFS_FS_INFO_FLAG_METADATA_UUID (1 << 2)
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struct btrfs_ioctl_fs_info_args {
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__u64 max_id; /* out */
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__u64 num_devices; /* out */
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__u8 fsid[BTRFS_FSID_SIZE]; /* out */
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__u32 nodesize; /* out */
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__u32 sectorsize; /* out */
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__u32 clone_alignment; /* out */
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/* See BTRFS_FS_INFO_FLAG_* */
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__u16 csum_type; /* out */
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__u16 csum_size; /* out */
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__u64 flags; /* in/out */
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__u64 generation; /* out */
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__u8 metadata_uuid[BTRFS_FSID_SIZE]; /* out */
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__u8 reserved[944]; /* pad to 1k */
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};
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.. list-table::
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:header-rows: 1
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@ -157,10 +184,14 @@ DATA STRUCTURES AND DEFINITIONS
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- Value
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* - BTRFS_UUID_SIZE
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- 16
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* - BTRFS_FSID_SIZE
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- 16
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* - BTRFS_SUBVOL_NAME_MAX
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- 4039
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* - BTRFS_PATH_NAME_MAX
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- 4087
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* - BTRFS_VOL_NAME_MAX
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- 255
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OVERVIEW
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--------
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@ -296,9 +327,9 @@ LIST OF IOCTLS
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* - BTRFS_IOC_DEV_INFO
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-
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-
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* - BTRFS_IOC_FS_INFO
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-
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-
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* - :ref:`BTRFS_IOC_FS_INFO<BTRFS_IOC_FS_INFO>`
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- get information about filesystem (device count, fsid, ...)
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- :ref:`struct btrfs_ioctl_fs_info_args<struct_btrfs_ioctl_fs_info_args>`
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* - BTRFS_IOC_BALANCE_V2
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-
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-
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@ -555,6 +586,26 @@ Change the flags of a subvolume.
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* - ioctl args
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- uint64_t, either 0 or `BTRFS_SUBVOL_RDONLY`
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.. _BTRFS_IOC_FS_INFO:
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BTRFS_IOC_FS_INFO
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~~~~~~~~~~~~~~~~~
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Read internal information about the filesystem. The data can be exchanged
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both ways and part of the structure could be optionally filled. The reserved
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bytes can be used to get new kind of information in the future, always
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depending on the flags set.
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.. list-table::
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:header-rows: 1
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* - Field
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- Description
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* - ioctl fd
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- file descriptor of any file/directory in the filesystem
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* - ioctl args
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- :ref:`struct btrfs_ioctl_fs_info_args<struct_btrfs_ioctl_fs_info_args>`
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.. _BTRFS_IOC_GET_SUBVOL_INFO:
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BTRFS_IOC_GET_SUBVOL_INFO
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|
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@ -52,6 +52,8 @@ OPTIONS
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change fsid stored as *metadata_uuid* to a randomly generated UUID,
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see also *-U*
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.. _btrfstune-feature-metadata-uuid:
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-M <UUID>
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(since kernel: 5.0)
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|
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@ -68,7 +68,7 @@ No other attributes are supported. For the complete list please refer to the
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XFLAGS
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^^^^^^
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There's overlap of letters assigned to the bits with the attributes, this list
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There's an overlap of letters assigned to the bits with the attributes, this list
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refers to what ``xfs_io(8)`` provides:
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i
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|
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@ -27,13 +27,15 @@ acl, noacl
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The support for ACL is build-time configurable (BTRFS_FS_POSIX_ACL) and
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mount fails if *acl* is requested but the feature is not compiled in.
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.. _mount-option-autodefrag:
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autodefrag, noautodefrag
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(since: 3.0, default: off)
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Enable automatic file defragmentation.
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When enabled, small random writes into files (in a range of tens of kilobytes,
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currently it's 64KiB) are detected and queued up for the defragmentation process.
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Not well suited for large database workloads.
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May not be well suited for large database workloads.
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The read latency may increase due to reading the adjacent blocks that make up the
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range for defragmentation, successive write will merge the blocks in the new
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@ -170,10 +172,12 @@ datasum, nodatasum
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The cost of checksumming of the blocks in memory is much lower than the IO,
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modern CPUs feature hardware support of the checksumming algorithm.
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.. _mount-option-degraded:
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degraded
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(default: off)
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Allow mounts with less devices than the RAID profile constraints
|
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Allow mounts with fewer devices than the RAID profile constraints
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require. A read-write mount (or remount) may fail when there are too many devices
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missing, for example if a stripe member is completely missing from RAID0.
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@ -261,12 +265,12 @@ flushoncommit, noflushoncommit
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one transaction commit.
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fragment=<type>
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(depends on compile-time option BTRFS_DEBUG, since: 4.4, default: off)
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(depends on compile-time option CONFIG_BTRFS_DEBUG, since: 4.4, default: off)
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A debugging helper to intentionally fragment given *type* of block groups. The
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type can be *data*, *metadata* or *all*. This mount option should not be used
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outside of debugging environments and is not recognized if the kernel config
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option *BTRFS_DEBUG* is not enabled.
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option *CONFIG_BTRFS_DEBUG* is not enabled.
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nologreplay
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(default: off, even read-only)
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|
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@ -287,8 +291,8 @@ max_inline=<bytes>
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with a K suffix (case insensitive). In practice, this value
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is limited by the filesystem block size (named *sectorsize* at mkfs time),
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and memory page size of the system. In case of sectorsize limit, there's
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some space unavailable due to leaf headers. For example, a 4KiB sectorsize,
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maximum size of inline data is about 3900 bytes.
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some space unavailable due to b-tree leaf headers. For example, a 4KiB
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sectorsize, maximum size of inline data is about 3900 bytes.
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Inlining can be completely turned off by specifying 0. This will increase data
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block slack if file sizes are much smaller than block size but will reduce
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|
|
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|
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@ -3,6 +3,11 @@ On-disk Format
|
|||
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This document describes the Btrfs on‐disk format.
|
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|
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.. note::
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This document contains outdated and incomplete information and has been
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copied from the original btrfs.wiki.kernel.org with little review.
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Overview
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~~~~~~~~
|
||||
|
||||
|
|
|
|||
|
|
@ -5,12 +5,13 @@ There's some common functionality found in many places like help, parsing
|
|||
values, sorting, extensible arrays, etc. Not all places are unified and use old
|
||||
code implementing it manually. Below is list of usable APIs that should be spread
|
||||
and updated where it's still not. A need for new API might emerge from
|
||||
cleanups, then it should appear here.
|
||||
cleanups, then it should appear here. The text below gives pointers and is not
|
||||
extensive, search the definitions and actual use in other code too.
|
||||
|
||||
Option parsing
|
||||
--------------
|
||||
|
||||
Files: common/help.h, common/parse-utils.h
|
||||
Files: :file:`common/help.h`, :file:`common/parse-utils.h`
|
||||
|
||||
Global options need to be processed and consumed by `clean_args_no_options`,
|
||||
argument count by `check_argc_*`, `usage_*` for handling usage.
|
||||
|
|
@ -18,6 +19,21 @@ argument count by `check_argc_*`, `usage_*` for handling usage.
|
|||
Options are parsed by `getopt` or `getopt_long`. Individual values from options
|
||||
are recognized by `parse_*`, basic types and custom types are supported.
|
||||
|
||||
Size unit pretty printing
|
||||
-------------------------
|
||||
|
||||
Files: :file:`common/units.h`
|
||||
|
||||
Many commands print byte sizes with suffixes and the output format can be
|
||||
affected by command line options. In the help text the options are specified by
|
||||
either `HELPINFO_UNITS_SHORT_LONG` (both long and short options) or just
|
||||
`HELPINFO_UNITS_LONG` in case the short option letters would conflict.
|
||||
|
||||
Automatic parsing of the options from *argv* is done by `get_unit_mode_from_arg`.
|
||||
Printing options is done by `pretty_size_mode` which takes the value and option
|
||||
mode. Default mode is human readable, the macros defining the modes are from
|
||||
`UNITS_*` namespace.
|
||||
|
||||
TODO
|
||||
----
|
||||
|
||||
|
|
@ -33,4 +49,3 @@ Undocumented or incomplete APIs:
|
|||
* common/string-table.h
|
||||
* common/string-table.h
|
||||
* common/task-utils.h
|
||||
* common/units.h
|
||||
|
|
|
|||
|
|
@ -19,14 +19,36 @@ Data types
|
|||
|
||||
Raw data types. Integer values are stored in little endian byte order.
|
||||
|
||||
- unsigned int 8bit (u8)
|
||||
- unsigned int 16bit (u16)
|
||||
- unsigned int 32bit (u32)
|
||||
- unsigned int 64bit (u64)
|
||||
- variable length binary data (data)
|
||||
- variable length string (string)
|
||||
- UUID, 16 bytes (uuid)
|
||||
- time specification, 64bit seconds, 32bit nanoseconds (timespec)
|
||||
.. list-table::
|
||||
:header-rows: 1
|
||||
|
||||
* - Meaning
|
||||
- Size
|
||||
- Name
|
||||
* - unsigned int
|
||||
- 8 bit
|
||||
- u8
|
||||
* - unsigned int
|
||||
- 16 bit
|
||||
- u16
|
||||
* - unsigned int
|
||||
- 32 bit
|
||||
- u32
|
||||
* - unsigned int
|
||||
- 64 bit
|
||||
- u64
|
||||
* - variable length binary data
|
||||
- variable
|
||||
- data
|
||||
* - variable length string
|
||||
- variable
|
||||
- string
|
||||
* - UUID
|
||||
- 16 bytes
|
||||
- uuid
|
||||
* - time specification
|
||||
- 64bit seconds, 32bit nanoseconds
|
||||
- timespec
|
||||
|
||||
Stream structure
|
||||
----------------
|
||||
|
|
|
|||
|
|
@ -79,6 +79,8 @@ OPTIONS
|
|||
|
||||
On multiple devices the default is *raid1*.
|
||||
|
||||
.. _mkfs-feature-mixed-bg:
|
||||
|
||||
-M|--mixed
|
||||
Normally the data and metadata block groups are isolated. The *mixed* mode
|
||||
will remove the isolation and store both types in the same block group type.
|
||||
|
|
@ -300,12 +302,29 @@ free-space-tree
|
|||
(default since btrfs-progs 5.15, kernel support since 4.5)
|
||||
|
||||
Enable the free space tree (mount option *space_cache=v2*) for persisting the
|
||||
free space cache.
|
||||
free space cache in a b-tree. This is built on top of the COW mechanism
|
||||
and has better performance than v1.
|
||||
|
||||
Offline conversion from filesystems that don't have this feature
|
||||
enabled at *mkfs* time is possible, see :doc:`btrfstune`.
|
||||
|
||||
Online conversion can be done by mounting with ``space_cache=v2``, this
|
||||
is sufficient to be done one time.
|
||||
|
||||
.. _mkfs-feature-block-group-tree:
|
||||
|
||||
block-group-tree
|
||||
(kernel support since 6.1)
|
||||
|
||||
Enable the block group tree to greatly reduce mount time for large filesystems.
|
||||
Enable a dedicated b-tree for block group items, this greatly reduces
|
||||
mount time for large filesystems due to better data locality that
|
||||
avoids seeking. On rotational devices the *large* size is considered
|
||||
starting from the 2-4TiB. Can be used on other types of devices (SSD,
|
||||
NVMe, ...) as well.
|
||||
|
||||
Offline conversion from filesystems that don't have this feature
|
||||
enabled at *mkfs* time is possible, see :doc:`btrfstune`. Online
|
||||
conversion is not possible.
|
||||
|
||||
.. _mkfs-section-profiles:
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue