2016-11-02 10:17:06 +00:00
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RBD Export & Import
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===================
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This is a file format of an RBD image or snapshot. It's a sparse format
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for the full image. There are three recording sections in the file.
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(1) Header.
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(2) Metadata.
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(3) Diffs.
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Header
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~~~~~~
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"rbd image v2\\n"
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Metadata records
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~~~~~~~~~~~~~~~~
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Every record has a one byte "tag" that identifies the record type,
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followed by length of data, and then some other data.
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Metadata records come in the first part of the image. Order is not
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important, as long as all the metadata records come before the data
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records.
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In v2, we have the following metadata in each section:
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(1 Bytes) tag.
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(8 Bytes) length.
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(n Bytes) data.
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In this way, we can skip the unrecognized tag.
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Image order
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-----------
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- u8: 'O'
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- le64: length of appending data (8)
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- le64: image order
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Image format
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------------
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- u8: 'F'
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- le64: length of appending data (8)
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- le64: image format
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Image Features
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--------------
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- u8: 'T'
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- le64: length of appending data (8)
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- le64: image features
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Image Stripe unit
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-----------------
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- u8: 'U'
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- le64: length of appending data (8)
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- le64: image striping unit
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Image Stripe count
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------------------
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- u8: 'C'
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- le64: length of appending data (8)
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- le64: image striping count
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2017-09-29 05:30:01 +00:00
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ImageMeta Key and Value
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-----------------------
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- u8: 'M'
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- le64: length of appending data (length of key + length of value + 4 * 2)
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- string: image-meta key
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- string: image-meta value
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2016-11-02 10:17:06 +00:00
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Final Record
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~~~~~~~~~~~~
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End
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---
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- u8: 'E'
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Diffs records
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~~~~~~~~~~~~~~~~~
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Record the all snapshots and the HEAD in this section.
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- le64: number of diffs
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- Diffs ...
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Detail please refer to rbd-diff.rst
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