Re: [PATCH 0/2] block/raw: implemented persistent dirty bitmap and ability to dump bitmap content via qapi

["Patrik Janoušek" <pj@patrikjanousek.cz>]

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Hello, thank you for the quick reply.

On 3/22/21 9:29 AM, Vladimir Sementsov-Ogievskiy wrote:
> 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}
I know about these commands, but they're useless to me without providing
access to the content of bitmap.
>
> 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)
Ok, I'll look at it.
>
>> 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.
Yes, I know. And that's the problem. The point of my bachelor thesis is
to implement a backup solution for the raw format.
>
>> 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
>>
>
>
Patrik Janoušek

IČO: 09291849


	+420 724 123 897 <tel:+420 724 123 897>

	pj@patrikjanousek.cz <mailto:pj@patrikjanousek.cz>


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