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btrfs-progs: docs: auto-repair editing
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Auto-repair on read | ||
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Data or metadata that are found to be damaged (e.g. because the checksum does | ||
not match) at the time they're read from a device can be salvaged in case the | ||
filesystem has another valid copy when using block group profile with redundancy | ||
(DUP, RAID1-like, RAID5/6). The correct data are returned to the user application | ||
and the damaged copy is replaced by it. When this happen a message is emitted | ||
to the system log. | ||
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If there are more copies of data and one of them is damaged but not read by | ||
user application then this is not detected. To verify all data and metadata | ||
copies there's :doc:`scrub<Scrub>` that needs to be started manually, automatic | ||
repairs happens in that case. | ||
If data or metadata that are found to be damaged at the time they’re read from a device, | ||
for example because the checksum does not match, they can be salvaged if the filesystem | ||
has another valid copy. This can be achieved by using a block group profile with redundancy | ||
like `DUP`, RAID1-like, or RAID5/6. | ||
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The correct data is returned to the user application and the damaged copy is replaced by it. | ||
When this happens, a message is emitted to the system log. | ||
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If there are multiple copies of data and one of them is damaged but not read by the user | ||
application, then this is not detected. | ||
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To ensure the verification and automatic repair of all data and metadata copies, the | ||
:doc:`scrub<Scrub>` operation must be initiated manually. |