39 lines
1.3 KiB
Plaintext
39 lines
1.3 KiB
Plaintext
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Qemu supports the NBD protocol, and has an internal NBD client (see
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block/nbd.c), an internal NBD server (see blockdev-nbd.c), and an
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external NBD server tool (see qemu-nbd.c). The common code is placed
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in nbd/*.
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The NBD protocol is specified here:
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https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md
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The following paragraphs describe some specific properties of NBD
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protocol realization in Qemu.
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= Metadata namespaces =
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Qemu supports the "base:allocation" metadata context as defined in the
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NBD protocol specification, and also defines an additional metadata
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namespace "qemu".
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== "qemu" namespace ==
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The "qemu" namespace currently contains only one type of context,
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related to exposing the contents of a dirty bitmap alongside the
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associated disk contents. That context has the following form:
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qemu:dirty-bitmap:<dirty-bitmap-export-name>
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Each dirty-bitmap metadata context defines only one flag for extents
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in reply for NBD_CMD_BLOCK_STATUS:
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bit 0: NBD_STATE_DIRTY, means that the extent is "dirty"
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For NBD_OPT_LIST_META_CONTEXT the following queries are supported
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in addition to "qemu:dirty-bitmap:<dirty-bitmap-export-name>":
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* "qemu:" - returns list of all available metadata contexts in the
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namespace.
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* "qemu:dirty-bitmap:" - returns list of all available dirty-bitmap
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metadata contexts.
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