search for: nbd_opt_info2

...ndshake for determining when the server supports > > NBD_CMD_FLAG_FAST_ZERO) >From an implementation point of view I prefer simple flags over having to implement a brand new option. We can always work out how to extend the flags field if we run out of flags. For example, by implementing NBD_OPT_INFO2 with a much bigger flags field. > > - a reference client and server implementation (probably both via qemu, > > since it was qemu that raised the problem in the first place) > > The last time we mentioned the possibility of advertising an initial > zero state, we debated whet...

While it may be counterintuitive at first, the introduction of NBD_CMD_WRITE_ZEROES and NBD_CMD_BLOCK_STATUS has caused a performance regression in qemu [1], when copying a sparse file. When the destination file must contain the same contents as the source, but it is not known in advance whether the destination started life with all zero content, then there are cases where it is faster to request