On 31.01.19 18:55, Kevin Wolf wrote: > There are use cases where raw images are given (e.g. existing physical > disks), but advanced features like dirty bitmaps or backing files are > wanted that require use of a proper image format like qcow2. > > This series adds an incompatible feature bit to qcow2 which allows to > use an external data file: Metadata is kept in the qcow2 file like > usual, but guest data is written to an external file. Clusters in the > data file are not reference counted, instead we use a flat layout where > host cluster offset == guest cluster offset. The external data file is > therefore readable as a raw image (though writing to it invalidates the > associated qcow2 metadata). Features that require refcounting such as > internal snapshots or compression are not supposed in such setups.
Overall the design to me looks as simple as it could be, which means there is equally little I could object to. I raised some technical things, but this is an RFC anyway, so, yeah. Looks good! About testing... I really don't know either. I'll think about it, maybe I come up with something. Max
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