Re: [Qemu-devel] [PATCH] mirror: add sync mode incremental to drive-mirror and blockdev-mirror

[Denis V. Lunev]

On 05/08/2017 10:35 PM, Stefan Hajnoczi wrote:
> On Thu, May 04, 2017 at 12:54:40PM +0200, Daniel Kucera wrote:
>
> Seems like a logical extension along the same lines as the backup block
> job's dirty bitmap sync mode.
>
>> parameter bitmap chooses existing dirtymap instead of newly created
>> in mirror_start_job
>>
>> Signed-off-by: Daniel Kucera <address@hidden>
Can you pls describe the use case pls in a bit more details.

For now this could be a bit strange:
- dirty bitmap, which can be found via bdrv_create_dirty_bitmap
  could be read-only or read-write, i.e. being modified by writes
  or be read-only, which should not be modified. Thus adding
  r/o bitmap to the mirror could result in interesting things.

Minimally we should prohibit usage of r/o bitmaps this way.

So, why to use mirror, not backup for the case?

Den