Difference between revisions of "Ploop/format"
< Ploop
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* Image consists of cluster blocks (default cluster block size is 1 MB). | * Image consists of cluster blocks (default cluster block size is 1 MB). | ||
* First there are some cluster blocks with BAT (Block Allocation Table), then there are some cluster blocks with data. | * First there are some cluster blocks with BAT (Block Allocation Table), then there are some cluster blocks with data. | ||
| − | * First 64 bytes of the first cluster | + | * First 64 bytes of the first cluster block is a header, described in [https://src.openvz.org/projects/OVZL/repos/ploop/browse/include/ploop1_image.h ploop1_image.h] |
* The rest of BAT is just an array of 4 byte slots. | * The rest of BAT is just an array of 4 byte slots. | ||
| − | * If a slot N contains value M, then a request to a cluster-block N of a /dev/ploopXXX device is redirected to a cluster-block M in an image file. | + | * If a slot N contains value M, then a request to a cluster-block N of a /dev/ploopXXX device is redirected to a cluster-block M in an image file. N is counted from 0, while M is counted from 1 (0 means block is not yet allocated). |
For the rest of the story, see sources. | For the rest of the story, see sources. | ||
[[Category: Storage]] | [[Category: Storage]] | ||
Revision as of 01:14, 22 December 2015
A ploop image file format is pretty simple.
- Image consists of cluster blocks (default cluster block size is 1 MB).
- First there are some cluster blocks with BAT (Block Allocation Table), then there are some cluster blocks with data.
- First 64 bytes of the first cluster block is a header, described in ploop1_image.h
- The rest of BAT is just an array of 4 byte slots.
- If a slot N contains value M, then a request to a cluster-block N of a /dev/ploopXXX device is redirected to a cluster-block M in an image file. N is counted from 0, while M is counted from 1 (0 means block is not yet allocated).
For the rest of the story, see sources.
