Hi Patrik!
20.03.2021 12:32, Patrik Janoušek wrote:
Currently, QEMU doesn't support persistent dirty bitmaps for raw format
That's right, we don't have such feature now.
and also dirty bitmaps are for internal use only, and cannot be accessed
using third-party applications.
And that's is not. Bitmaps are accessible through bitmap QMP API
block-dirty-bitmap-{add,remove,clear,merge}
And to retrieve the context of dirty bitmap you can export it through NBD
protocol (see bitmaps argument in nbd specific options of block-export-add
command)
These facts are very limiting
in case someone would like to develop their own backup tool becaouse
without access to the dirty bitmap it would be possible to implement
only full backups.
We do have external incremental backups, based on Qemu bitmap API. But it
depends of course on qcow2 persistent bitmaps feature.
And without persistent dirty bitmaps, it wouldn't
be possible to keep track of changed data after QEMU is restarted. And
this is exactly what I do as a part of my bachelor thesis. I've
developed a tool that is able to create incremental backups of drives
in raw format that are LVM volumes (ability to create snapshot is
required).
Please keep in mind that this is my first submission to such a large
project and also the first time when I send patch over the email.
So I hope I did it correctly.
Patrik Janoušek (2):
block/raw: added support of persistent dirty bitmaps
qapi: implementation of the block-dirty-bitmap-dump command
block/meson.build | 1 +
block/monitor/bitmap-qmp-cmds.c | 61 ++++++++
block/raw-format-bitmap.c | 163 ++++++++++++++++++++
block/raw-format.c | 256 ++++++++++++++++++++++++++++++--
block/raw-format.h | 50 +++++++
qapi/block-core.json | 64 +++++++-
6 files changed, 583 insertions(+), 12 deletions(-)
create mode 100644 block/raw-format-bitmap.c
create mode 100644 block/raw-format.h
--
Best regards,
Vladimir
