2018-06-09 18:17:58 +03:00
|
|
|
Qemu supports the NBD protocol, and has an internal NBD client (see
|
|
|
|
|
block/nbd.c), an internal NBD server (see blockdev-nbd.c), and an
|
|
|
|
|
external NBD server tool (see qemu-nbd.c). The common code is placed
|
|
|
|
|
in nbd/*.
|
|
|
|
|
|
|
|
|
|
The NBD protocol is specified here:
|
|
|
|
|
https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md
|
|
|
|
|
|
|
|
|
|
The following paragraphs describe some specific properties of NBD
|
|
|
|
|
protocol realization in Qemu.
|
|
|
|
|
|
|
|
|
|
= Metadata namespaces =
|
|
|
|
|
|
|
|
|
|
Qemu supports the "base:allocation" metadata context as defined in the
|
|
|
|
|
NBD protocol specification, and also defines an additional metadata
|
|
|
|
|
namespace "qemu".
|
|
|
|
|
|
|
|
|
|
== "qemu" namespace ==
|
|
|
|
|
|
|
|
|
|
The "qemu" namespace currently contains only one type of context,
|
|
|
|
|
related to exposing the contents of a dirty bitmap alongside the
|
|
|
|
|
associated disk contents. That context has the following form:
|
|
|
|
|
|
|
|
|
|
qemu:dirty-bitmap:<dirty-bitmap-export-name>
|
|
|
|
|
|
|
|
|
|
Each dirty-bitmap metadata context defines only one flag for extents
|
|
|
|
|
in reply for NBD_CMD_BLOCK_STATUS:
|
|
|
|
|
|
|
|
|
|
bit 0: NBD_STATE_DIRTY, means that the extent is "dirty"
|
|
|
|
|
|
|
|
|
|
For NBD_OPT_LIST_META_CONTEXT the following queries are supported
|
|
|
|
|
in addition to "qemu:dirty-bitmap:<dirty-bitmap-export-name>":
|
|
|
|
|
|
|
|
|
|
* "qemu:" - returns list of all available metadata contexts in the
|
|
|
|
|
namespace.
|
|
|
|
|
* "qemu:dirty-bitmap:" - returns list of all available dirty-bitmap
|
|
|
|
|
metadata contexts.
|
2018-12-15 16:53:04 +03:00
|
|
|
|
|
|
|
|
= Features by version =
|
|
|
|
|
|
|
|
|
|
The following list documents which qemu version first implemented
|
|
|
|
|
various features (both as a server exposing the feature, and as a
|
|
|
|
|
client taking advantage of the feature when present), to make it
|
|
|
|
|
easier to plan for cross-version interoperability. Note that in
|
|
|
|
|
several cases, the initial release containing a feature may require
|
|
|
|
|
additional patches from the corresponding stable branch to fix bugs in
|
|
|
|
|
the operation of that feature.
|
|
|
|
|
|
|
|
|
|
* 2.6: NBD_OPT_STARTTLS with TLS X.509 Certificates
|
|
|
|
|
* 2.8: NBD_CMD_WRITE_ZEROES
|
|
|
|
|
* 2.10: NBD_OPT_GO, NBD_INFO_BLOCK
|
|
|
|
|
* 2.11: NBD_OPT_STRUCTURED_REPLY
|
|
|
|
|
* 2.12: NBD_CMD_BLOCK_STATUS for "base:allocation"
|
|
|
|
|
* 3.0: NBD_OPT_STARTTLS with TLS Pre-Shared Keys (PSK),
|
|
|
|
|
NBD_CMD_BLOCK_STATUS for "qemu:dirty-bitmap:", NBD_CMD_CACHE
|
