On 4 Apr 2016, at 14:56, Eric Blake <eblake@...696...> wrote: > Question - qemu already has the notion of an nbd server that can be > configured to explicitly check for large repetitions of zero during > NBD_CMD_WRITE, and create holes in the corresponding file as a result > (basically because qemu is compensating for NBD_CMD_WRITE_ZEROES not > being part of the protocol yet, so that the destination file can still > be sparse even though lots of zeroes were sent over the wire). Should we > also allow servers to accept NBD_CMD_FLAG_NO_HOLE during NBD_CMD_WRITE > as an explicit request to NOT perform the magic of searching for large > runs of zeroes, but to just write everything as written? Seems a good idea, but I'd make it a SHOULD rather than a MUST. IE it's saying "please don't make a hole" but really this is up to the nbd server. This is true in any case, as the underlying filing system could create a hole. -- Alex Bligh
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