projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | RBD Export & Import |
| 2 | =================== | |
| 3 | ||
| 4 | This is a file format of an RBD image or snapshot. It's a sparse format | |
| 5 | for the full image. There are three recording sections in the file. | |
| 6 | ||
| 7 | (1) Header. | |
| 8 | (2) Metadata. | |
| 9 | (3) Diffs. | |
| 10 | ||
| 11 | Header | |
| 12 | ~~~~~~ | |
| 13 | ||
| 14 | "rbd image v2\\n" | |
| 15 | ||
| 16 | Metadata records | |
| 17 | ~~~~~~~~~~~~~~~~ | |
| 18 | ||
| 19 | Every record has a one byte "tag" that identifies the record type, | |
| 20 | followed by length of data, and then some other data. | |
| 21 | ||
| 22 | Metadata records come in the first part of the image. Order is not | |
| 23 | important, as long as all the metadata records come before the data | |
| 24 | records. | |
| 25 | ||
| 26 | In v2, we have the following metadata in each section: | |
| 27 | (1 Bytes) tag. | |
| 28 | (8 Bytes) length. | |
| 29 | (n Bytes) data. | |
| 30 | ||
| 31 | In this way, we can skip the unrecognized tag. | |
| 32 | ||
| 33 | Image order | |
| 34 | ----------- | |
| 35 | ||
| 36 | - u8: 'O' | |
| 37 | - le64: length of appending data (8) | |
| 38 | - le64: image order | |
| 39 | ||
| 40 | Image format | |
| 41 | ------------ | |
| 42 | ||
| 43 | - u8: 'F' | |
| 44 | - le64: length of appending data (8) | |
| 45 | - le64: image format | |
| 46 | ||
| 47 | Image Features | |
| 48 | -------------- | |
| 49 | ||
| 50 | - u8: 'T' | |
| 51 | - le64: length of appending data (8) | |
| 52 | - le64: image features | |
| 53 | ||
| 54 | Image Stripe unit | |
| 55 | ----------------- | |
| 56 | ||
| 57 | - u8: 'U' | |
| 58 | - le64: length of appending data (8) | |
| 59 | - le64: image striping unit | |
| 60 | ||
| 61 | Image Stripe count | |
| 62 | ------------------ | |
| 63 | ||
| 64 | - u8: 'C' | |
| 65 | - le64: length of appending data (8) | |
| 66 | - le64: image striping count | |
| 67 | ||
| 68 | Final Record | |
| 69 | ~~~~~~~~~~~~ | |
| 70 | ||
| 71 | End | |
| 72 | --- | |
| 73 | ||
| 74 | - u8: 'E' | |
| 75 | ||
| 76 | ||
| 77 | Diffs records | |
| 78 | ~~~~~~~~~~~~~~~~~ | |
| 79 | Record the all snapshots and the HEAD in this section. | |
| 80 | ||
| 81 | - le64: number of diffs | |
| 82 | - Diffs ... | |
| 83 | ||
| 84 | Detail please refer to rbd-diff.rst |