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Modern way is using blockdev-add + blockdev-backup, which provides a lot more control on how target is opened. As example of drive-backup problems consider the following: User of drive-backup expects that target will be opened in the same cache and aio mode as source. Corresponding logic is in drive_backup_prepare(), where we take bs->open_flags of source. It works rather bad if source was added by blockdev-add. Assume source is qcow2 image. On blockdev-add we should specify aio and cache options for file child of qcow2 node. What happens next: drive_backup_prepare() looks at bs->open_flags of qcow2 source node. But there no BDRV_O_NOCAHE neither BDRV_O_NATIVE_AIO: BDRV_O_NOCAHE is places in bs->file->bs->open_flags, and BDRV_O_NATIVE_AIO is nowhere, as file-posix parse options and simply set s->use_linux_aio. The documentation is updated in a minimal way, so that drive-backup is noted only as a deprecated command, and blockdev-backup used in most of places. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> |
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| .. | ||
| barrier.rst | ||
| bitmaps.rst | ||
| dbus-vmstate.rst | ||
| dbus.rst | ||
| firmware.json | ||
| index.rst | ||
| live-block-operations.rst | ||
| nbd.txt | ||
| parallels.txt | ||
| pr-helper.rst | ||
| prl-xml.txt | ||
| qcow2.txt | ||
| qed_spec.txt | ||
| qemu-ga-ref.rst | ||
| qemu-ga.rst | ||
| qemu-qmp-ref.rst | ||
| qemu-storage-daemon-qmp-ref.rst | ||
| qmp-intro.txt | ||
| qmp-spec.txt | ||
| vhost-user-gpu.rst | ||
| vhost-user.json | ||
| vhost-user.rst | ||
| vhost-vdpa.rst | ||
| vnc-ledstate-Pseudo-encoding.txt | ||