mirror of
https://github.com/ceph/ceph
synced 2024-12-15 16:07:00 +00:00
85 lines
1.4 KiB
ReStructuredText
85 lines
1.4 KiB
ReStructuredText
RBD Export & Import
|
|
===================
|
|
|
|
This is a file format of an RBD image or snapshot. It's a sparse format
|
|
for the full image. There are three recording sections in the file.
|
|
|
|
(1) Header.
|
|
(2) Metadata.
|
|
(3) Diffs.
|
|
|
|
Header
|
|
~~~~~~
|
|
|
|
"rbd image v2\\n"
|
|
|
|
Metadata records
|
|
~~~~~~~~~~~~~~~~
|
|
|
|
Every record has a one byte "tag" that identifies the record type,
|
|
followed by length of data, and then some other data.
|
|
|
|
Metadata records come in the first part of the image. Order is not
|
|
important, as long as all the metadata records come before the data
|
|
records.
|
|
|
|
In v2, we have the following metadata in each section:
|
|
(1 Bytes) tag.
|
|
(8 Bytes) length.
|
|
(n Bytes) data.
|
|
|
|
In this way, we can skip the unrecognized tag.
|
|
|
|
Image order
|
|
-----------
|
|
|
|
- u8: 'O'
|
|
- le64: length of appending data (8)
|
|
- le64: image order
|
|
|
|
Image format
|
|
------------
|
|
|
|
- u8: 'F'
|
|
- le64: length of appending data (8)
|
|
- le64: image format
|
|
|
|
Image Features
|
|
--------------
|
|
|
|
- u8: 'T'
|
|
- le64: length of appending data (8)
|
|
- le64: image features
|
|
|
|
Image Stripe unit
|
|
-----------------
|
|
|
|
- u8: 'U'
|
|
- le64: length of appending data (8)
|
|
- le64: image striping unit
|
|
|
|
Image Stripe count
|
|
------------------
|
|
|
|
- u8: 'C'
|
|
- le64: length of appending data (8)
|
|
- le64: image striping count
|
|
|
|
Final Record
|
|
~~~~~~~~~~~~
|
|
|
|
End
|
|
---
|
|
|
|
- u8: 'E'
|
|
|
|
|
|
Diffs records
|
|
~~~~~~~~~~~~~~~~~
|
|
Record the all snapshots and the HEAD in this section.
|
|
|
|
- le64: number of diffs
|
|
- Diffs ...
|
|
|
|
Detail please refer to rbd-diff.rst
|