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Re: [Qemu-devel] [PATCH v4 00/18] bitmaps: introduce 'bitmap' sync mode
From: |
John Snow |
Subject: |
Re: [Qemu-devel] [PATCH v4 00/18] bitmaps: introduce 'bitmap' sync mode |
Date: |
Mon, 22 Jul 2019 13:21:02 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 |
On 7/22/19 8:17 AM, Fabian Grünbichler wrote:
> On Tue, Jul 09, 2019 at 07:25:32PM -0400, John Snow wrote:
>> This series adds a new "BITMAP" sync mode that is meant to replace the
>> existing "INCREMENTAL" sync mode.
>>
>> This mode can have its behavior modified by issuing any of three bitmap sync
>> modes, passed as arguments to the job.
>>
>> The three bitmap sync modes are:
>> - ON-SUCCESS: This is an alias for the old incremental mode. The bitmap is
>> conditionally synchronized based on the return code of the job
>> upon completion.
>> - NEVER: This is, effectively, the differential backup mode. It never clears
>> the bitmap, as the name suggests.
>> - ALWAYS: Here is the new, exciting thing. The bitmap is always synchronized,
>> even on failure. On success, this is identical to incremental, but
>> on failure it clears only the bits that were copied successfully.
>> This can be used to "resume" incremental backups from later points
>> in times.
>>
>> I wrote this series by accident on my way to implement incremental mode
>> for mirror, but this happened first -- the problem is that Mirror mode
>> uses its existing modes in a very particular way; and this was the best
>> way to add bitmap support into the mirror job properly.
>>
>> [...]
>>
>> Future work:
>> [..]
>> - Add these modes to Mirror. (Done*, but needs tests.)
>
> are these mirror patches available somehwere for testing in combination
> with this series? your bitmaps branch does not seem to contain them ;)
>
> we've been experimenting with Ma Haocong's patch (v4 from February) to add
> "incremental"/differential sync to drive-mirror recently with positive
> results so far, and this sounds like it is another attempt at getting
> this properly integrated into Qemu.
>
Not available quite yet; I added it in fairly hastily but haven't done
the testing I want to do yet, so I wouldn't feel comfortable sharing it
before I do my own due diligence on it. Give me a chance to polish it so
that the testing effort isn't wasted :)
Can you share some of your use-cases for how you are using the
"incremental mirror" so far? It might be useful for the patch
justification if I can point to production use cases. (And good for
allocating time, too.)
--js
- [Qemu-devel] [PATCH v4 09/18] block/dirty-bitmap: add bdrv_dirty_bitmap_merge_internal, (continued)
- [Qemu-devel] [PATCH v4 09/18] block/dirty-bitmap: add bdrv_dirty_bitmap_merge_internal, John Snow, 2019/07/09
- [Qemu-devel] [PATCH v4 18/18] block/backup: loosen restriction on readonly bitmaps, John Snow, 2019/07/09
- [Qemu-devel] [PATCH v4 17/18] iotests: add test 257 for bitmap-mode backups, John Snow, 2019/07/09
- Re: [Qemu-devel] [PATCH v4 00/18] bitmaps: introduce 'bitmap' sync mode, Max Reitz, 2019/07/10
- Re: [Qemu-devel] [PATCH v4 00/18] bitmaps: introduce 'bitmap' sync mode, John Snow, 2019/07/15
- Re: [Qemu-devel] [PATCH v4 00/18] bitmaps: introduce 'bitmap' sync mode, Fabian Grünbichler, 2019/07/22
- Re: [Qemu-devel] [PATCH v4 00/18] bitmaps: introduce 'bitmap' sync mode,
John Snow <=