projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | RBD Incremental Backup |
| 2 | ====================== | |
| 3 | ||
| 4 | This is a simple streaming file format for representing a diff between | |
| 5 | two snapshots (or a snapshot and the head) of an RBD image. | |
| 6 | ||
| 7 | Header | |
| 8 | ~~~~~~ | |
| 9 | ||
| 10 | "rbd diff v1\\n" | |
| 11 | ||
| 12 | Metadata records | |
| 13 | ~~~~~~~~~~~~~~~~ | |
| 14 | ||
| 15 | Every record has a one byte "tag" that identifies the record type, | |
| 16 | followed by some other data. | |
| 17 | ||
| 18 | Metadata records come in the first part of the image. Order is not | |
| 19 | important, as long as all the metadata records come before the data | |
| 20 | records. | |
| 21 | ||
| 22 | From snap | |
| 23 | --------- | |
| 24 | ||
| 25 | - u8: 'f' | |
| 26 | - le32: snap name length | |
| 27 | - snap name | |
| 28 | ||
| 29 | To snap | |
| 30 | ------- | |
| 31 | ||
| 32 | - u8: 't' | |
| 33 | - le32: snap name length | |
| 34 | - snap name | |
| 35 | ||
| 36 | Size | |
| 37 | ---- | |
| 38 | ||
| 39 | - u8: 's' | |
| 40 | - le64: (ending) image size | |
| 41 | ||
| 42 | Data Records | |
| 43 | ~~~~~~~~~~~~ | |
| 44 | ||
| 45 | These records come in the second part of the sequence. | |
| 46 | ||
| 47 | Updated data | |
| 48 | ------------ | |
| 49 | ||
| 50 | - u8: 'w' | |
| 51 | - le64: offset | |
| 52 | - le64: length | |
| 53 | - length bytes of actual data | |
| 54 | ||
| 55 | Zero data | |
| 56 | --------- | |
| 57 | ||
| 58 | - u8: 'z' | |
| 59 | - le64: offset | |
| 60 | - le64: length | |
| 61 | ||
| 62 | ||
| 63 | Final Record | |
| 64 | ~~~~~~~~~~~~ | |
| 65 | ||
| 66 | End | |
| 67 | --- | |
| 68 | ||
| 69 | - u8: 'e' | |
| 70 | ||
| 71 | ||
| 72 | Header | |
| 73 | ~~~~~~ | |
| 74 | ||
| 75 | "rbd diff v2\\n" | |
| 76 | ||
| 77 | Metadata records | |
| 78 | ~~~~~~~~~~~~~~~~ | |
| 79 | ||
| 80 | Every record has a one byte "tag" that identifies the record type, | |
| 81 | followed by length of data, and then some other data. | |
| 82 | ||
| 83 | Metadata records come in the first part of the image. Order is not | |
| 84 | important, as long as all the metadata records come before the data | |
| 85 | records. | |
| 86 | ||
| 87 | In v2, we have the following metadata in each section: | |
| 88 | (1 Bytes) tag. | |
| 89 | (8 Bytes) length. | |
| 90 | (n Bytes) data. | |
| 91 | ||
| 92 | In this way, we can skip the unrecognized tag. | |
| 93 | ||
| 94 | From snap | |
| 95 | --------- | |
| 96 | ||
| 97 | - u8: 'f' | |
| 98 | - le64: length of appending data (4 + length) | |
| 99 | - le32: snap name length | |
| 100 | - snap name | |
| 101 | ||
| 102 | To snap | |
| 103 | ------- | |
| 104 | ||
| 105 | - u8: 't' | |
| 106 | - le64: length of appending data (4 + length) | |
| 107 | - le32: snap name length | |
| 108 | - snap name | |
| 109 | ||
| 110 | Size | |
| 111 | ---- | |
| 112 | ||
| 113 | - u8: 's' | |
| 114 | - le64: length of appending data (8) | |
| 115 | - le64: (ending) image size | |
| 116 | ||
| 117 | Data Records | |
| 118 | ~~~~~~~~~~~~ | |
| 119 | ||
| 120 | These records come in the second part of the sequence. | |
| 121 | ||
| 122 | Updated data | |
| 123 | ------------ | |
| 124 | ||
| 125 | - u8: 'w' | |
| 126 | - le64: length of appending data (8 + 8 + length) | |
| 127 | - le64: offset | |
| 128 | - le64: length | |
| 129 | - length bytes of actual data | |
| 130 | ||
| 131 | Zero data | |
| 132 | --------- | |
| 133 | ||
| 134 | - u8: 'z' | |
| 135 | - le64: length of appending data (8 + 8) | |
| 136 | - le64: offset | |
| 137 | - le64: length | |
| 138 | ||
| 139 | ||
| 140 | Final Record | |
| 141 | ~~~~~~~~~~~~ | |
| 142 | ||
| 143 | End | |
| 144 | --- | |
| 145 | ||
| 146 | - u8: 'e' |